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	$35.69	3.562%	$36.9613	$36.96	$36.95	$37.00
Purchase #2	$242.53	9.118%	$264.6439	$264.64	$264.65	$264.60
Purchase #3	$140.98	7.618%	$151.7199	$151.72	$151.70	$151.70
Purchase #4	$162.81	6.839%	$173.9446	$173.94	$173.95	$173.90
Purchase #5	$32.79	7.150%	$35.1345	$35.13	$35.15	$35.10
Purchase #6	$197.59	3.332%	$204.1737	$204.17	$204.15	$204.20
Purchase #7	$131.85	13.595%	$149.775	$149.78	$149.80	$149.80
7 purchase totals =	$944.24		$1,016.3529	$1,016.34	$1,016.35	$1,016.30