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	$37.27	11.599%	$41.5929	$41.59	$41.60	$41.60
Purchase #2	$204.58	11.157%	$227.405	$227.41	$227.40	$227.40
Purchase #3	$165.90	5.437%	$174.92	$174.92	$174.90	$174.90
Purchase #4	$194.78	4.109%	$202.7835	$202.78	$202.80	$202.80
Purchase #5	$35.47	11.637%	$39.5976	$39.60	$39.60	$39.60
Purchase #6	$181.59	12.728%	$204.7028	$204.70	$204.70	$204.70
Purchase #7	$111.91	13.503%	$127.0212	$127.02	$127.00	$127.00
7 purchase totals =	$931.50		$1,018.0230	$1,018.02	$1,018.00	$1,018.00