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	$14.76	13.216%	$16.7107	$16.71	$16.70	$16.70
Purchase #2	$71.76	6.109%	$76.1438	$76.14	$76.15	$76.10
Purchase #3	$46.97	13.185%	$53.163	$53.16	$53.15	$53.20
Purchase #4	$81.47	5.202%	$85.7081	$85.71	$85.70	$85.70
Purchase #5	$65.74	11.261%	$73.143	$73.14	$73.15	$73.10
Purchase #6	$180.25	11.245%	$200.5191	$200.52	$200.50	$200.50
Purchase #7	$46.43	9.698%	$50.9328	$50.93	$50.95	$50.90
7 purchase totals =	$507.38		$556.3205	$556.31	$556.30	$556.20