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	$90.82	11.563%	$101.3215	$101.32	$101.30	$101.30
Purchase #2	$121.58	8.815%	$132.2973	$132.30	$132.30	$132.30
Purchase #3	$169.85	8.428%	$184.165	$184.17	$184.15	$184.20
Purchase #4	$90.97	10.263%	$100.3063	$100.31	$100.30	$100.30
Purchase #5	$179.76	11.640%	$200.6841	$200.68	$200.70	$200.70
Purchase #6	$28.73	11.456%	$32.0213	$32.02	$32.00	$32.00
Purchase #7	$60.83	4.834%	$63.7705	$63.77	$63.75	$63.80
7 purchase totals =	$742.54		$814.5660	$814.57	$814.50	$814.60