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	$86.49	3.143%	$89.2084	$89.21	$89.20	$89.20
Purchase #2	$69.75	12.790%	$78.671	$78.67	$78.65	$78.70
Purchase #3	$67.63	6.357%	$71.9292	$71.93	$71.95	$71.90
Purchase #4	$42.66	13.574%	$48.4507	$48.45	$48.45	$48.50
Purchase #5	$46.50	9.514%	$50.924	$50.92	$50.90	$50.90
Purchase #6	$114.76	10.713%	$127.0542	$127.05	$127.05	$127.10
Purchase #7	$21.46	12.745%	$24.1951	$24.20	$24.20	$24.20
7 purchase totals =	$449.25		$490.4326	$490.43	$490.40	$490.50