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	$137.31	7.139%	$147.1126	$147.11	$147.10	$147.10
Purchase #2	$231.51	4.505%	$241.9395	$241.94	$241.95	$241.90
Purchase #3	$219.32	5.192%	$230.7071	$230.71	$230.70	$230.70
Purchase #4	$38.48	4.569%	$40.2382	$40.24	$40.25	$40.20
Purchase #5	$133.62	6.201%	$141.9058	$141.91	$141.90	$141.90
Purchase #6	$108.36	13.780%	$123.292	$123.29	$123.30	$123.30
Purchase #7	$127.41	6.366%	$135.5209	$135.52	$135.50	$135.50
7 purchase totals =	$996.01		$1,060.7161	$1,060.72	$1,060.70	$1,060.60