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	$111.38	13.811%	$126.7627	$126.76	$126.75	$126.80
Purchase #2	$17.91	5.473%	$18.8902	$18.89	$18.90	$18.90
Purchase #3	$50.60	6.354%	$53.8151	$53.82	$53.80	$53.80
Purchase #4	$233.54	4.501%	$244.0516	$244.05	$244.05	$244.10
Purchase #5	$160.95	12.511%	$181.0865	$181.09	$181.10	$181.10
Purchase #6	$38.75	8.384%	$41.9988	$42.00	$42.00	$42.00
Purchase #7	$56.83	7.378%	$61.0229	$61.02	$61.00	$61.00
7 purchase totals =	$669.96		$727.6278	$727.63	$727.60	$727.70