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	$192.97	9.362%	$211.0359	$211.04	$211.05	$211.00
Purchase #2	$202.77	12.362%	$227.8364	$227.84	$227.85	$227.80
Purchase #3	$189.61	13.468%	$215.1467	$215.15	$215.15	$215.10
Purchase #4	$220.94	13.178%	$250.0555	$250.06	$250.05	$250.10
Purchase #5	$100.70	10.400%	$111.1728	$111.17	$111.15	$111.20
Purchase #6	$148.62	12.294%	$166.8913	$166.89	$166.90	$166.90
Purchase #7	$122.56	13.332%	$138.8997	$138.90	$138.90	$138.90
7 purchase totals =	$1,178.17		$1,321.0383	$1,321.05	$1,321.05	$1,321.00