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	$63.43	3.873%	$65.8866	$65.89	$65.90	$65.90
Purchase #2	$69.31	3.129%	$71.4787	$71.48	$71.50	$71.50
Purchase #3	$112.36	9.154%	$122.6454	$122.65	$122.65	$122.60
Purchase #4	$190.76	10.437%	$210.6696	$210.67	$210.65	$210.70
Purchase #5	$210.69	6.867%	$225.1581	$225.16	$225.15	$225.20
Purchase #6	$121.75	7.546%	$130.9373	$130.94	$130.95	$130.90
Purchase #7	$105.35	5.776%	$111.435	$111.44	$111.45	$111.40
7 purchase totals =	$873.65		$938.2107	$938.23	$938.25	$938.20