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	$167.55	7.731%	$180.5033	$180.50	$180.50	$180.50
Purchase #2	$177.57	4.129%	$184.9019	$184.90	$184.90	$184.90
Purchase #3	$58.72	4.488%	$61.3554	$61.36	$61.35	$61.40
Purchase #4	$198.49	8.610%	$215.58	$215.58	$215.60	$215.60
Purchase #5	$131.48	4.256%	$137.0758	$137.08	$137.10	$137.10
Purchase #6	$91.34	10.743%	$101.1527	$101.15	$101.15	$101.20
Purchase #7	$84.72	6.789%	$90.4716	$90.47	$90.45	$90.50
7 purchase totals =	$909.87		$971.0407	$971.04	$971.05	$971.20