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	$90.69	12.543%	$102.0652	$102.07	$102.05	$102.10
Purchase #2	$73.42	5.826%	$77.6974	$77.70	$77.70	$77.70
Purchase #3	$82.78	6.172%	$87.8892	$87.89	$87.90	$87.90
Purchase #4	$70.98	11.140%	$78.8872	$78.89	$78.90	$78.90
Purchase #5	$10.78	12.835%	$12.1636	$12.16	$12.15	$12.20
Purchase #6	$37.77	13.487%	$42.864	$42.86	$42.85	$42.90
Purchase #7	$89.66	3.241%	$92.5659	$92.57	$92.55	$92.60
7 purchase totals =	$456.08		$494.1325	$494.14	$494.10	$494.30