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	$193.47	12.384%	$217.4293	$217.43	$217.45	$217.40
Purchase #2	$51.96	3.771%	$53.9194	$53.92	$53.90	$53.90
Purchase #3	$96.72	13.111%	$109.401	$109.40	$109.40	$109.40
Purchase #4	$64.67	9.171%	$70.6009	$70.60	$70.60	$70.60
Purchase #5	$110.40	6.409%	$117.4755	$117.48	$117.50	$117.50
Purchase #6	$103.43	5.490%	$109.1083	$109.11	$109.10	$109.10
Purchase #7	$209.44	13.207%	$237.1007	$237.10	$237.10	$237.10
7 purchase totals =	$830.09		$915.0351	$915.04	$915.05	$915.00