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	$41.97	10.363%	$46.3194	$46.32	$46.30	$46.30
Purchase #2	$150.33	7.131%	$161.05	$161.05	$161.05	$161.10
Purchase #3	$161.45	7.714%	$173.9043	$173.90	$173.90	$173.90
Purchase #4	$31.99	6.470%	$34.0598	$34.06	$34.05	$34.10
Purchase #5	$245.72	7.564%	$264.3063	$264.31	$264.30	$264.30
Purchase #6	$37.38	8.252%	$40.4646	$40.46	$40.45	$40.50
Purchase #7	$72.77	6.518%	$77.5131	$77.51	$77.50	$77.50
7 purchase totals =	$741.61		$797.6175	$797.61	$797.55	$797.70