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	$34.88	4.491%	$36.4465	$36.45	$36.45	$36.40
Purchase #2	$168.79	9.814%	$185.3551	$185.36	$185.35	$185.40
Purchase #3	$186.77	12.393%	$209.9164	$209.92	$209.90	$209.90
Purchase #4	$223.75	4.446%	$233.6979	$233.70	$233.70	$233.70
Purchase #5	$60.86	6.243%	$64.6595	$64.66	$64.65	$64.70
Purchase #6	$212.46	10.215%	$234.1628	$234.16	$234.15	$234.20
Purchase #7	$37.55	5.452%	$39.5972	$39.60	$39.60	$39.60
7 purchase totals =	$925.06		$1,003.8354	$1,003.85	$1,003.80	$1,003.90