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	$158.64	6.341%	$168.6994	$168.70	$168.70	$168.70
Purchase #2	$147.48	5.666%	$155.8362	$155.84	$155.85	$155.80
Purchase #3	$124.68	7.841%	$134.4562	$134.46	$134.45	$134.50
Purchase #4	$165.74	12.142%	$185.8642	$185.86	$185.85	$185.90
Purchase #5	$48.25	8.349%	$52.2784	$52.28	$52.30	$52.30
Purchase #6	$77.64	6.238%	$82.4832	$82.48	$82.50	$82.50
Purchase #7	$154.49	11.753%	$172.6472	$172.65	$172.65	$172.60
7 purchase totals =	$876.92		$952.2648	$952.27	$952.30	$952.30