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	$94.77	8.821%	$103.1297	$103.13	$103.15	$103.10
Purchase #2	$26.42	7.222%	$28.3281	$28.33	$28.35	$28.30
Purchase #3	$126.99	10.231%	$139.9823	$139.98	$140.00	$140.00
Purchase #4	$130.27	4.673%	$136.3575	$136.36	$136.35	$136.40
Purchase #5	$98.74	10.556%	$109.163	$109.16	$109.15	$109.20
Purchase #6	$177.96	10.405%	$196.4767	$196.48	$196.50	$196.50
Purchase #7	$135.57	13.226%	$153.5005	$153.50	$153.50	$153.50
7 purchase totals =	$790.72		$866.9378	$866.94	$867.00	$867.00