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	$64.65	12.180%	$72.5244	$72.52	$72.50	$72.50
Purchase #2	$180.86	10.864%	$200.5086	$200.51	$200.50	$200.50
Purchase #3	$236.33	11.426%	$263.3331	$263.33	$263.35	$263.30
Purchase #4	$247.81	13.467%	$281.1826	$281.18	$281.20	$281.20
Purchase #5	$69.46	13.216%	$78.6398	$78.64	$78.65	$78.60
Purchase #6	$222.99	8.134%	$241.128	$241.13	$241.15	$241.10
Purchase #7	$143.70	3.480%	$148.7008	$148.70	$148.70	$148.70
7 purchase totals =	$1,165.80		$1,286.0173	$1,286.01	$1,286.05	$1,285.90