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	$10.31	11.250%	$11.4699	$11.47	$11.45	$11.50
Purchase #2	$203.32	6.299%	$216.1271	$216.13	$216.15	$216.10
Purchase #3	$67.96	7.323%	$72.9367	$72.94	$72.95	$72.90
Purchase #4	$227.88	9.418%	$249.3417	$249.34	$249.35	$249.30
Purchase #5	$114.55	12.322%	$128.6649	$128.66	$128.65	$128.70
Purchase #6	$218.38	13.832%	$248.5863	$248.59	$248.60	$248.60
Purchase #7	$229.86	6.774%	$245.4307	$245.43	$245.45	$245.40
7 purchase totals =	$1,072.26		$1,172.5573	$1,172.56	$1,172.60	$1,172.50