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	$242.79	8.823%	$264.2114	$264.21	$264.20	$264.20
Purchase #2	$96.90	8.595%	$105.2286	$105.23	$105.25	$105.20
Purchase #3	$244.26	11.761%	$272.9874	$272.99	$273.00	$273.00
Purchase #4	$81.93	12.690%	$92.3269	$92.33	$92.35	$92.30
Purchase #5	$233.69	9.130%	$255.0259	$255.03	$255.05	$255.00
Purchase #6	$10.71	3.677%	$11.1038	$11.10	$11.10	$11.10
Purchase #7	$140.51	8.374%	$152.2763	$152.28	$152.30	$152.30
7 purchase totals =	$1,050.79		$1,153.1603	$1,153.17	$1,153.25	$1,153.10