Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.70	13.517%	$194.9087	$194.91	$194.90	$194.90
Purchase #2	$93.36	12.574%	$105.0991	$105.10	$105.10	$105.10
Purchase #3	$233.44	6.732%	$249.1552	$249.16	$249.15	$249.20
Purchase #4	$139.29	12.237%	$156.3349	$156.33	$156.35	$156.30
Purchase #5	$173.33	11.269%	$192.8626	$192.86	$192.85	$192.90
Purchase #6	$193.78	12.874%	$218.7272	$218.73	$218.75	$218.70
Purchase #7	$115.96	13.404%	$131.5033	$131.50	$131.50	$131.50
7 purchase totals =	$1,120.86		$1,248.5910	$1,248.59	$1,248.60	$1,248.60