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	$177.29	5.248%	$186.5942	$186.59	$186.60	$186.60
Purchase #2	$97.70	5.306%	$102.884	$102.88	$102.90	$102.90
Purchase #3	$64.84	9.502%	$71.0011	$71.00	$71.00	$71.00
Purchase #4	$194.59	7.165%	$208.5324	$208.53	$208.55	$208.50
Purchase #5	$66.62	7.145%	$71.38	$71.38	$71.40	$71.40
Purchase #6	$48.78	3.560%	$50.5166	$50.52	$50.50	$50.50
Purchase #7	$111.56	13.333%	$126.4343	$126.43	$126.45	$126.40
7 purchase totals =	$761.38		$817.3426	$817.33	$817.40	$817.30