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	$212.72	4.778%	$222.8838	$222.88	$222.90	$222.90
Purchase #2	$104.32	13.610%	$118.518	$118.52	$118.50	$118.50
Purchase #3	$44.94	7.831%	$48.4593	$48.46	$48.45	$48.50
Purchase #4	$233.82	13.213%	$264.7146	$264.71	$264.70	$264.70
Purchase #5	$250.88	13.729%	$285.3233	$285.32	$285.30	$285.30
Purchase #6	$48.61	3.498%	$50.3104	$50.31	$50.30	$50.30
Purchase #7	$222.94	5.422%	$235.0278	$235.03	$235.05	$235.00
7 purchase totals =	$1,118.23		$1,225.2372	$1,225.23	$1,225.20	$1,225.20