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	$35.78	3.279%	$36.9532	$36.95	$36.95	$37.00
Purchase #2	$141.27	7.117%	$151.3242	$151.32	$151.30	$151.30
Purchase #3	$33.29	7.437%	$35.7658	$35.77	$35.75	$35.80
Purchase #4	$42.64	3.106%	$43.9644	$43.96	$43.95	$44.00
Purchase #5	$59.37	10.774%	$65.7665	$65.77	$65.75	$65.80
Purchase #6	$118.28	12.467%	$133.026	$133.03	$133.05	$133.00
Purchase #7	$89.60	7.120%	$95.9795	$95.98	$96.00	$96.00
7 purchase totals =	$520.23		$562.7796	$562.78	$562.75	$562.90