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	$59.41	9.838%	$65.2548	$65.25	$65.25	$65.30
Purchase #2	$192.35	13.670%	$218.6442	$218.64	$218.65	$218.60
Purchase #3	$216.48	10.459%	$239.1216	$239.12	$239.10	$239.10
Purchase #4	$34.67	9.169%	$37.8489	$37.85	$37.85	$37.80
Purchase #5	$98.36	12.428%	$110.5842	$110.58	$110.60	$110.60
Purchase #6	$243.33	13.732%	$276.7441	$276.74	$276.75	$276.70
Purchase #7	$142.50	6.640%	$151.962	$151.96	$151.95	$152.00
7 purchase totals =	$987.10		$1,100.1598	$1,100.14	$1,100.15	$1,100.10