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	$219.54	11.286%	$244.3173	$244.32	$244.30	$244.30
Purchase #2	$59.89	13.336%	$67.8769	$67.88	$67.90	$67.90
Purchase #3	$59.42	8.128%	$64.2497	$64.25	$64.25	$64.20
Purchase #4	$178.94	5.333%	$188.4829	$188.48	$188.50	$188.50
Purchase #5	$88.91	6.502%	$94.6909	$94.69	$94.70	$94.70
Purchase #6	$152.43	13.355%	$172.787	$172.79	$172.80	$172.80
Purchase #7	$152.92	4.530%	$159.8473	$159.85	$159.85	$159.80
7 purchase totals =	$912.05		$992.2520	$992.26	$992.30	$992.20