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	$234.92	12.689%	$264.729	$264.73	$264.75	$264.70
Purchase #2	$199.78	11.317%	$222.3891	$222.39	$222.40	$222.40
Purchase #3	$179.35	10.210%	$197.6616	$197.66	$197.65	$197.70
Purchase #4	$85.58	5.462%	$90.2544	$90.25	$90.25	$90.30
Purchase #5	$75.31	9.267%	$82.289	$82.29	$82.30	$82.30
Purchase #6	$20.75	4.404%	$21.6638	$21.66	$21.65	$21.70
Purchase #7	$150.53	8.113%	$162.7425	$162.74	$162.75	$162.70
7 purchase totals =	$946.22		$1,041.7294	$1,041.72	$1,041.75	$1,041.80