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	$179.43	12.279%	$201.4622	$201.46	$201.45	$201.50
Purchase #2	$206.53	13.447%	$234.3021	$234.30	$234.30	$234.30
Purchase #3	$75.57	9.192%	$82.5164	$82.52	$82.50	$82.50
Purchase #4	$185.42	12.532%	$208.6568	$208.66	$208.65	$208.70
Purchase #5	$42.70	10.222%	$47.0648	$47.06	$47.05	$47.10
Purchase #6	$62.69	13.473%	$71.1362	$71.14	$71.15	$71.10
Purchase #7	$86.29	4.633%	$90.2878	$90.29	$90.30	$90.30
7 purchase totals =	$838.63		$935.4263	$935.43	$935.40	$935.50