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	$86.51	7.643%	$93.122	$93.12	$93.10	$93.10
Purchase #2	$28.74	12.433%	$32.3132	$32.31	$32.30	$32.30
Purchase #3	$147.62	3.532%	$152.8339	$152.83	$152.85	$152.80
Purchase #4	$59.97	8.185%	$64.8785	$64.88	$64.90	$64.90
Purchase #5	$32.97	12.693%	$37.1549	$37.15	$37.15	$37.20
Purchase #6	$145.28	7.250%	$155.8128	$155.81	$155.80	$155.80
Purchase #7	$109.28	10.647%	$120.915	$120.92	$120.90	$120.90
7 purchase totals =	$610.37		$657.0303	$657.02	$657.00	$657.00