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	$167.75	8.485%	$181.9836	$181.98	$182.00	$182.00
Purchase #2	$45.71	10.722%	$50.611	$50.61	$50.60	$50.60
Purchase #3	$92.45	6.754%	$98.6941	$98.69	$98.70	$98.70
Purchase #4	$160.33	3.512%	$165.9608	$165.96	$165.95	$166.00
Purchase #5	$47.67	4.870%	$49.9915	$49.99	$50.00	$50.00
Purchase #6	$58.85	4.140%	$61.2864	$61.29	$61.30	$61.30
Purchase #7	$53.56	9.383%	$58.5855	$58.59	$58.60	$58.60
7 purchase totals =	$626.32		$667.1129	$667.11	$667.15	$667.20