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	$164.48	13.821%	$187.2128	$187.21	$187.20	$187.20
Purchase #2	$69.84	12.719%	$78.7229	$78.72	$78.70	$78.70
Purchase #3	$230.25	11.424%	$256.5538	$256.55	$256.55	$256.60
Purchase #4	$45.54	11.608%	$50.8263	$50.83	$50.85	$50.80
Purchase #5	$11.36	3.404%	$11.7467	$11.75	$11.75	$11.70
Purchase #6	$80.69	13.419%	$91.5178	$91.52	$91.50	$91.50
Purchase #7	$83.52	5.183%	$87.8488	$87.85	$87.85	$87.80
7 purchase totals =	$685.68		$764.4291	$764.43	$764.40	$764.30