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	$215.77	11.615%	$240.8317	$240.83	$240.85	$240.80
Purchase #2	$104.85	12.239%	$117.6826	$117.68	$117.70	$117.70
Purchase #3	$95.51	11.701%	$106.6856	$106.69	$106.70	$106.70
Purchase #4	$166.81	12.599%	$187.8264	$187.83	$187.85	$187.80
Purchase #5	$58.47	5.325%	$61.5835	$61.58	$61.60	$61.60
Purchase #6	$84.70	8.751%	$92.1121	$92.11	$92.10	$92.10
Purchase #7	$188.76	4.326%	$196.9258	$196.93	$196.95	$196.90
7 purchase totals =	$914.87		$1,003.6477	$1,003.65	$1,003.75	$1,003.60