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	$149.85	7.650%	$161.3135	$161.31	$161.30	$161.30
Purchase #2	$153.29	5.111%	$161.1247	$161.12	$161.10	$161.10
Purchase #3	$106.63	8.754%	$115.9644	$115.96	$115.95	$116.00
Purchase #4	$131.39	7.814%	$141.6568	$141.66	$141.65	$141.70
Purchase #5	$127.27	11.128%	$141.4326	$141.43	$141.45	$141.40
Purchase #6	$182.68	7.564%	$196.4979	$196.50	$196.50	$196.50
Purchase #7	$18.91	9.121%	$20.6348	$20.63	$20.65	$20.60
7 purchase totals =	$870.02		$938.6247	$938.61	$938.60	$938.60