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	$143.32	5.527%	$151.2413	$151.24	$151.25	$151.20
Purchase #2	$208.37	13.579%	$236.6646	$236.66	$236.65	$236.70
Purchase #3	$196.56	13.743%	$223.5732	$223.57	$223.55	$223.60
Purchase #4	$233.95	4.222%	$243.8274	$243.83	$243.85	$243.80
Purchase #5	$33.83	4.404%	$35.3199	$35.32	$35.30	$35.30
Purchase #6	$203.47	12.856%	$229.6281	$229.63	$229.65	$229.60
Purchase #7	$213.84	7.717%	$230.342	$230.34	$230.35	$230.30
7 purchase totals =	$1,233.34		$1,350.5965	$1,350.59	$1,350.60	$1,350.50