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	$181.49	11.371%	$202.1272	$202.13	$202.15	$202.10
Purchase #2	$140.30	4.874%	$147.1382	$147.14	$147.15	$147.10
Purchase #3	$189.82	3.400%	$196.2739	$196.27	$196.25	$196.30
Purchase #4	$11.94	8.143%	$12.9123	$12.91	$12.90	$12.90
Purchase #5	$68.95	4.302%	$71.9162	$71.92	$71.90	$71.90
Purchase #6	$104.59	9.493%	$114.5187	$114.52	$114.50	$114.50
Purchase #7	$139.61	11.184%	$155.224	$155.22	$155.20	$155.20
7 purchase totals =	$836.70		$900.1105	$900.11	$900.05	$900.00