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	$168.57	8.120%	$182.2579	$182.26	$182.25	$182.30
Purchase #2	$231.53	8.335%	$250.828	$250.83	$250.85	$250.80
Purchase #3	$152.41	13.537%	$173.0417	$173.04	$173.05	$173.00
Purchase #4	$55.71	5.840%	$58.9635	$58.96	$58.95	$59.00
Purchase #5	$238.56	9.185%	$260.4717	$260.47	$260.45	$260.50
Purchase #6	$150.32	5.218%	$158.1637	$158.16	$158.15	$158.20
Purchase #7	$60.33	11.582%	$67.3174	$67.32	$67.30	$67.30
7 purchase totals =	$1,057.43		$1,151.0439	$1,151.04	$1,151.00	$1,151.10