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	$115.49	13.728%	$131.3445	$131.34	$131.35	$131.30
Purchase #2	$67.77	13.501%	$76.9196	$76.92	$76.90	$76.90
Purchase #3	$82.69	3.406%	$85.5064	$85.51	$85.50	$85.50
Purchase #4	$101.79	3.395%	$105.2458	$105.25	$105.25	$105.20
Purchase #5	$116.50	8.154%	$125.9994	$126.00	$126.00	$126.00
Purchase #6	$237.83	11.381%	$264.8974	$264.90	$264.90	$264.90
Purchase #7	$193.72	9.773%	$212.6523	$212.65	$212.65	$212.70
7 purchase totals =	$915.79		$1,002.5654	$1,002.57	$1,002.55	$1,002.50