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	$179.40	6.692%	$191.4054	$191.41	$191.40	$191.40
Purchase #2	$74.28	4.417%	$77.5609	$77.56	$77.55	$77.60
Purchase #3	$131.73	13.229%	$149.1566	$149.16	$149.15	$149.20
Purchase #4	$126.52	12.244%	$142.0111	$142.01	$142.00	$142.00
Purchase #5	$50.47	8.748%	$54.8851	$54.89	$54.90	$54.90
Purchase #6	$95.60	8.463%	$103.6906	$103.69	$103.70	$103.70
Purchase #7	$80.43	11.395%	$89.595	$89.60	$89.60	$89.60
7 purchase totals =	$738.43		$808.3047	$808.32	$808.30	$808.40