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	$91.79	5.348%	$96.6989	$96.70	$96.70	$96.70
Purchase #2	$181.51	10.665%	$200.868	$200.87	$200.85	$200.90
Purchase #3	$141.35	7.447%	$151.8763	$151.88	$151.90	$151.90
Purchase #4	$84.78	7.119%	$90.8155	$90.82	$90.80	$90.80
Purchase #5	$156.52	9.562%	$171.4864	$171.49	$171.50	$171.50
Purchase #6	$51.92	5.566%	$54.8099	$54.81	$54.80	$54.80
Purchase #7	$201.34	8.633%	$218.7217	$218.72	$218.70	$218.70
7 purchase totals =	$909.21		$985.2767	$985.29	$985.25	$985.30