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	$40.95	10.599%	$45.2903	$45.29	$45.30	$45.30
Purchase #2	$83.35	7.137%	$89.2987	$89.30	$89.30	$89.30
Purchase #3	$171.43	3.871%	$178.0661	$178.07	$178.05	$178.10
Purchase #4	$129.49	11.578%	$144.4824	$144.48	$144.50	$144.50
Purchase #5	$116.97	10.642%	$129.4179	$129.42	$129.40	$129.40
Purchase #6	$140.50	11.119%	$156.1222	$156.12	$156.10	$156.10
Purchase #7	$214.58	11.335%	$238.9026	$238.90	$238.90	$238.90
7 purchase totals =	$897.27		$981.5802	$981.58	$981.55	$981.60