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	$239.71	4.538%	$250.588	$250.59	$250.60	$250.60
Purchase #2	$11.95	6.227%	$12.6941	$12.69	$12.70	$12.70
Purchase #3	$232.66	13.579%	$264.2529	$264.25	$264.25	$264.30
Purchase #4	$42.66	6.417%	$45.3975	$45.40	$45.40	$45.40
Purchase #5	$152.32	4.661%	$159.4196	$159.42	$159.40	$159.40
Purchase #6	$152.64	7.572%	$164.1979	$164.20	$164.20	$164.20
Purchase #7	$91.53	6.152%	$97.1609	$97.16	$97.15	$97.20
7 purchase totals =	$923.47		$993.7109	$993.71	$993.70	$993.80