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	$239.66	9.449%	$262.3055	$262.31	$262.30	$262.30
Purchase #2	$27.74	4.292%	$28.9306	$28.93	$28.95	$28.90
Purchase #3	$31.83	10.413%	$35.1445	$35.14	$35.15	$35.10
Purchase #4	$87.55	4.134%	$91.1693	$91.17	$91.15	$91.20
Purchase #5	$122.47	4.650%	$128.1649	$128.16	$128.15	$128.20
Purchase #6	$168.90	9.325%	$184.6499	$184.65	$184.65	$184.60
Purchase #7	$52.49	7.504%	$56.4288	$56.43	$56.45	$56.40
7 purchase totals =	$730.64		$786.7935	$786.79	$786.80	$786.70