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	$115.89	10.316%	$127.8452	$127.85	$127.85	$127.80
Purchase #2	$214.66	13.509%	$243.6584	$243.66	$243.65	$243.70
Purchase #3	$196.82	7.781%	$212.1346	$212.13	$212.15	$212.10
Purchase #4	$184.80	5.730%	$195.389	$195.39	$195.40	$195.40
Purchase #5	$111.56	12.377%	$125.3678	$125.37	$125.35	$125.40
Purchase #6	$197.57	12.593%	$222.45	$222.45	$222.45	$222.50
Purchase #7	$70.89	10.516%	$78.3448	$78.34	$78.35	$78.30
7 purchase totals =	$1,092.19		$1,205.1898	$1,205.19	$1,205.20	$1,205.20