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	$113.88	12.344%	$127.9373	$127.94	$127.95	$127.90
Purchase #2	$78.31	5.713%	$82.7839	$82.78	$82.80	$82.80
Purchase #3	$18.36	8.282%	$19.8806	$19.88	$19.90	$19.90
Purchase #4	$179.26	7.356%	$192.4464	$192.45	$192.45	$192.40
Purchase #5	$153.43	7.573%	$165.0493	$165.05	$165.05	$165.00
Purchase #6	$108.43	4.312%	$113.1055	$113.11	$113.10	$113.10
Purchase #7	$144.49	9.496%	$158.2108	$158.21	$158.20	$158.20
7 purchase totals =	$796.16		$859.4138	$859.42	$859.45	$859.30