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	$32.34	5.553%	$34.1358	$34.14	$34.15	$34.10
Purchase #2	$200.54	12.259%	$225.1242	$225.12	$225.10	$225.10
Purchase #3	$137.86	5.771%	$145.8159	$145.82	$145.80	$145.80
Purchase #4	$174.38	9.248%	$190.5067	$190.51	$190.50	$190.50
Purchase #5	$32.57	3.515%	$33.7148	$33.71	$33.70	$33.70
Purchase #6	$247.28	8.801%	$269.0431	$269.04	$269.05	$269.00
Purchase #7	$162.90	3.434%	$168.494	$168.49	$168.50	$168.50
7 purchase totals =	$987.87		$1,066.8345	$1,066.83	$1,066.80	$1,066.70