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	$165.53	4.141%	$172.3846	$172.38	$172.40	$172.40
Purchase #2	$141.80	7.873%	$152.9639	$152.96	$152.95	$153.00
Purchase #3	$187.50	10.547%	$207.2756	$207.28	$207.30	$207.30
Purchase #4	$156.82	8.862%	$170.7174	$170.72	$170.70	$170.70
Purchase #5	$122.34	4.559%	$127.9175	$127.92	$127.90	$127.90
Purchase #6	$91.53	7.442%	$98.3417	$98.34	$98.35	$98.30
Purchase #7	$134.33	3.703%	$139.3042	$139.30	$139.30	$139.30
7 purchase totals =	$999.85		$1,068.9049	$1,068.90	$1,068.90	$1,068.90