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	$89.58	12.786%	$101.0337	$101.03	$101.05	$101.00
Purchase #2	$189.89	11.200%	$211.1577	$211.16	$211.15	$211.20
Purchase #3	$89.93	7.207%	$96.4113	$96.41	$96.40	$96.40
Purchase #4	$139.63	9.738%	$153.2272	$153.23	$153.25	$153.20
Purchase #5	$58.29	13.874%	$66.3772	$66.38	$66.40	$66.40
Purchase #6	$248.68	6.389%	$264.5682	$264.57	$264.55	$264.60
Purchase #7	$152.48	9.619%	$167.1471	$167.15	$167.15	$167.10
7 purchase totals =	$968.48		$1,059.9224	$1,059.93	$1,059.95	$1,059.90