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	$166.66	10.445%	$184.0676	$184.07	$184.05	$184.10
Purchase #2	$52.65	12.263%	$59.1065	$59.11	$59.10	$59.10
Purchase #3	$240.53	9.231%	$262.7333	$262.73	$262.75	$262.70
Purchase #4	$61.72	6.104%	$65.4874	$65.49	$65.50	$65.50
Purchase #5	$35.83	7.834%	$38.6369	$38.64	$38.65	$38.60
Purchase #6	$211.90	8.510%	$229.9327	$229.93	$229.95	$229.90
Purchase #7	$127.25	7.709%	$137.0597	$137.06	$137.05	$137.10
7 purchase totals =	$896.54		$977.0241	$977.03	$977.05	$977.00