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	$127.67	5.351%	$134.5016	$134.50	$134.50	$134.50
Purchase #2	$175.93	10.257%	$193.9751	$193.98	$194.00	$194.00
Purchase #3	$151.27	9.413%	$165.509	$165.51	$165.50	$165.50
Purchase #4	$172.34	7.164%	$184.6864	$184.69	$184.70	$184.70
Purchase #5	$40.27	8.740%	$43.7896	$43.79	$43.80	$43.80
Purchase #6	$21.90	13.254%	$24.8026	$24.80	$24.80	$24.80
Purchase #7	$236.53	13.830%	$269.2421	$269.24	$269.25	$269.20
7 purchase totals =	$925.91		$1,016.5064	$1,016.51	$1,016.55	$1,016.50