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	$31.26	10.719%	$34.6108	$34.61	$34.60	$34.60
Purchase #2	$102.66	10.489%	$113.428	$113.43	$113.45	$113.40
Purchase #3	$238.72	6.215%	$253.5564	$253.56	$253.55	$253.60
Purchase #4	$55.80	7.294%	$59.8701	$59.87	$59.85	$59.90
Purchase #5	$223.96	8.354%	$242.6696	$242.67	$242.65	$242.70
Purchase #6	$230.49	10.326%	$254.2904	$254.29	$254.30	$254.30
Purchase #7	$171.95	9.572%	$188.4091	$188.41	$188.40	$188.40
7 purchase totals =	$1,054.84		$1,146.8344	$1,146.84	$1,146.80	$1,146.90