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	$56.88	13.113%	$64.3387	$64.34	$64.35	$64.30
Purchase #2	$238.58	5.287%	$251.1937	$251.19	$251.20	$251.20
Purchase #3	$89.76	7.334%	$96.343	$96.34	$96.35	$96.30
Purchase #4	$228.34	12.122%	$256.0194	$256.02	$256.00	$256.00
Purchase #5	$165.66	11.835%	$185.2659	$185.27	$185.25	$185.30
Purchase #6	$12.89	4.357%	$13.4516	$13.45	$13.45	$13.50
Purchase #7	$124.86	9.678%	$136.944	$136.94	$136.95	$136.90
7 purchase totals =	$916.97		$1,003.5563	$1,003.55	$1,003.55	$1,003.50