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	$73.29	7.463%	$78.7596	$78.76	$78.75	$78.80
Purchase #2	$16.57	13.495%	$18.8061	$18.81	$18.80	$18.80
Purchase #3	$28.78	13.699%	$32.7226	$32.72	$32.70	$32.70
Purchase #4	$247.41	10.770%	$274.0561	$274.06	$274.05	$274.10
Purchase #5	$237.90	11.396%	$265.0111	$265.01	$265.00	$265.00
Purchase #6	$42.45	12.580%	$47.7902	$47.79	$47.80	$47.80
Purchase #7	$40.44	7.394%	$43.4301	$43.43	$43.45	$43.40
7 purchase totals =	$686.84		$760.5758	$760.58	$760.55	$760.60