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	$223.84	10.435%	$247.1977	$247.20	$247.20	$247.20
Purchase #2	$218.91	11.409%	$243.8854	$243.89	$243.90	$243.90
Purchase #3	$91.63	4.210%	$95.4876	$95.49	$95.50	$95.50
Purchase #4	$72.33	11.190%	$80.4237	$80.42	$80.40	$80.40
Purchase #5	$133.64	8.659%	$145.2119	$145.21	$145.20	$145.20
Purchase #6	$179.62	13.700%	$204.2279	$204.23	$204.25	$204.20
Purchase #7	$101.53	9.417%	$111.0911	$111.09	$111.10	$111.10
7 purchase totals =	$1,021.50		$1,127.5253	$1,127.53	$1,127.55	$1,127.50