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	$41.72	8.359%	$45.2074	$45.21	$45.20	$45.20
Purchase #2	$32.29	9.260%	$35.2801	$35.28	$35.30	$35.30
Purchase #3	$168.25	12.210%	$188.7933	$188.79	$188.80	$188.80
Purchase #4	$57.29	9.790%	$62.8987	$62.90	$62.90	$62.90
Purchase #5	$83.78	6.148%	$88.9308	$88.93	$88.95	$88.90
Purchase #6	$85.35	13.173%	$96.5932	$96.59	$96.60	$96.60
Purchase #7	$206.83	5.244%	$217.6762	$217.68	$217.70	$217.70
7 purchase totals =	$675.51		$735.3797	$735.38	$735.45	$735.40