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	$156.41	7.105%	$167.5229	$167.52	$167.50	$167.50
Purchase #2	$96.45	9.231%	$105.3533	$105.35	$105.35	$105.40
Purchase #3	$53.38	3.238%	$55.1084	$55.11	$55.10	$55.10
Purchase #4	$84.38	13.818%	$96.0396	$96.04	$96.05	$96.00
Purchase #5	$65.97	9.690%	$72.3625	$72.36	$72.35	$72.40
Purchase #6	$33.94	9.646%	$37.2139	$37.21	$37.20	$37.20
Purchase #7	$82.55	6.236%	$87.6978	$87.70	$87.70	$87.70
7 purchase totals =	$573.08		$621.2984	$621.29	$621.25	$621.30