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	$111.27	12.202%	$124.8472	$124.85	$124.85	$124.80
Purchase #2	$28.80	13.874%	$32.7957	$32.80	$32.80	$32.80
Purchase #3	$39.49	4.111%	$41.1134	$41.11	$41.10	$41.10
Purchase #4	$241.33	11.336%	$268.6872	$268.69	$268.70	$268.70
Purchase #5	$88.33	10.102%	$97.2531	$97.25	$97.25	$97.30
Purchase #6	$85.60	5.755%	$90.5263	$90.53	$90.55	$90.50
Purchase #7	$182.43	12.458%	$205.1571	$205.16	$205.15	$205.20
7 purchase totals =	$777.25		$860.3800	$860.39	$860.40	$860.40