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	$55.41	9.314%	$60.5709	$60.57	$60.55	$60.60
Purchase #2	$225.49	11.475%	$251.365	$251.37	$251.35	$251.40
Purchase #3	$94.41	9.813%	$103.6745	$103.67	$103.65	$103.70
Purchase #4	$124.80	3.294%	$128.9109	$128.91	$128.90	$128.90
Purchase #5	$226.50	10.329%	$249.8952	$249.90	$249.90	$249.90
Purchase #6	$66.52	7.511%	$71.5163	$71.52	$71.50	$71.50
Purchase #7	$244.54	8.599%	$265.568	$265.57	$265.55	$265.60
7 purchase totals =	$1,037.67		$1,131.5008	$1,131.51	$1,131.40	$1,131.60