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	$127.94	7.178%	$137.1235	$137.12	$137.10	$137.10
Purchase #2	$20.56	10.215%	$22.6602	$22.66	$22.65	$22.70
Purchase #3	$238.78	10.619%	$264.136	$264.14	$264.15	$264.10
Purchase #4	$247.42	3.204%	$255.3473	$255.35	$255.35	$255.30
Purchase #5	$97.68	12.391%	$109.7835	$109.78	$109.80	$109.80
Purchase #6	$74.58	7.873%	$80.4517	$80.45	$80.45	$80.50
Purchase #7	$192.97	11.689%	$215.5263	$215.53	$215.55	$215.50
7 purchase totals =	$999.93		$1,085.0285	$1,085.03	$1,085.05	$1,085.00