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	$133.31	6.472%	$141.9378	$141.94	$141.95	$141.90
Purchase #2	$55.61	12.458%	$62.5379	$62.54	$62.55	$62.50
Purchase #3	$94.67	6.170%	$100.5111	$100.51	$100.50	$100.50
Purchase #4	$95.78	13.238%	$108.4594	$108.46	$108.45	$108.50
Purchase #5	$86.92	11.653%	$97.0488	$97.05	$97.05	$97.00
Purchase #6	$49.91	7.142%	$53.4746	$53.47	$53.45	$53.50
Purchase #7	$243.62	6.861%	$260.3348	$260.33	$260.35	$260.30
7 purchase totals =	$759.82		$824.3044	$824.30	$824.30	$824.20