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	$200.85	4.498%	$209.8842	$209.88	$209.90	$209.90
Purchase #2	$91.64	5.431%	$96.617	$96.62	$96.60	$96.60
Purchase #3	$135.50	11.680%	$151.3264	$151.33	$151.35	$151.30
Purchase #4	$231.91	6.497%	$246.9772	$246.98	$247.00	$247.00
Purchase #5	$166.78	3.311%	$172.3021	$172.30	$172.30	$172.30
Purchase #6	$77.34	7.465%	$83.1134	$83.11	$83.10	$83.10
Purchase #7	$96.71	3.729%	$100.3163	$100.32	$100.30	$100.30
7 purchase totals =	$1,000.73		$1,060.5366	$1,060.54	$1,060.55	$1,060.50