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	$59.75	4.473%	$62.4226	$62.42	$62.40	$62.40
Purchase #2	$234.50	11.443%	$261.3338	$261.33	$261.35	$261.30
Purchase #3	$238.89	9.157%	$260.7652	$260.77	$260.75	$260.80
Purchase #4	$241.46	6.404%	$256.9231	$256.92	$256.90	$256.90
Purchase #5	$31.28	11.140%	$34.7646	$34.76	$34.75	$34.80
Purchase #6	$46.34	13.244%	$52.4773	$52.48	$52.50	$52.50
Purchase #7	$231.63	5.193%	$243.6585	$243.66	$243.65	$243.70
7 purchase totals =	$1,083.85		$1,172.3451	$1,172.34	$1,172.30	$1,172.40