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	$34.89	6.379%	$37.1156	$37.12	$37.10	$37.10
Purchase #2	$210.59	5.427%	$222.0187	$222.02	$222.00	$222.00
Purchase #3	$6.48	10.462%	$7.1579	$7.16	$7.15	$7.20
Purchase #4	$229.38	11.513%	$255.7885	$255.79	$255.80	$255.80
Purchase #5	$56.52	5.711%	$59.7479	$59.75	$59.75	$59.70
Purchase #6	$176.43	13.748%	$200.6856	$200.69	$200.70	$200.70
Purchase #7	$220.76	4.375%	$230.4183	$230.42	$230.40	$230.40
7 purchase totals =	$935.05		$1,012.9325	$1,012.95	$1,012.90	$1,012.90