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	$179.29	11.267%	$199.4906	$199.49	$199.50	$199.50
Purchase #2	$173.56	12.418%	$195.1127	$195.11	$195.10	$195.10
Purchase #3	$76.52	8.176%	$82.7763	$82.78	$82.80	$82.80
Purchase #4	$205.27	9.753%	$225.29	$225.29	$225.30	$225.30
Purchase #5	$105.46	4.426%	$110.1277	$110.13	$110.15	$110.10
Purchase #6	$26.73	6.671%	$28.5132	$28.51	$28.50	$28.50
Purchase #7	$80.54	12.609%	$90.6953	$90.70	$90.70	$90.70
7 purchase totals =	$847.37		$932.0058	$932.01	$932.05	$932.00