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	$53.89	5.703%	$56.9633	$56.96	$56.95	$57.00
Purchase #2	$187.87	4.493%	$196.311	$196.31	$196.30	$196.30
Purchase #3	$151.59	12.627%	$170.7313	$170.73	$170.75	$170.70
Purchase #4	$233.31	13.866%	$265.6608	$265.66	$265.65	$265.70
Purchase #5	$70.30	13.304%	$79.6527	$79.65	$79.65	$79.70
Purchase #6	$224.89	4.790%	$235.6622	$235.66	$235.65	$235.70
Purchase #7	$103.36	7.689%	$111.3074	$111.31	$111.30	$111.30
7 purchase totals =	$1,025.21		$1,116.2887	$1,116.28	$1,116.25	$1,116.40