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	$95.55	4.333%	$99.6902	$99.69	$99.70	$99.70
Purchase #2	$77.34	10.264%	$85.2782	$85.28	$85.30	$85.30
Purchase #3	$51.90	8.479%	$56.3006	$56.30	$56.30	$56.30
Purchase #4	$49.85	12.198%	$55.9307	$55.93	$55.95	$55.90
Purchase #5	$52.97	6.586%	$56.4586	$56.46	$56.45	$56.50
Purchase #6	$137.51	6.846%	$146.9239	$146.92	$146.90	$146.90
Purchase #7	$12.55	8.498%	$13.6165	$13.62	$13.60	$13.60
7 purchase totals =	$477.67		$514.1987	$514.20	$514.20	$514.20