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	$28.97	11.400%	$32.2726	$32.27	$32.25	$32.30
Purchase #2	$239.81	8.158%	$259.3737	$259.37	$259.35	$259.40
Purchase #3	$41.86	11.717%	$46.7647	$46.76	$46.75	$46.80
Purchase #4	$134.40	6.157%	$142.675	$142.68	$142.70	$142.70
Purchase #5	$161.87	13.838%	$184.2696	$184.27	$184.25	$184.30
Purchase #6	$119.57	6.817%	$127.7211	$127.72	$127.70	$127.70
Purchase #7	$240.79	13.118%	$272.3768	$272.38	$272.40	$272.40
7 purchase totals =	$967.27		$1,065.4535	$1,065.45	$1,065.40	$1,065.60