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	$133.96	10.367%	$147.8476	$147.85	$147.85	$147.80
Purchase #2	$83.91	8.611%	$91.1355	$91.14	$91.15	$91.10
Purchase #3	$158.89	4.327%	$165.7652	$165.77	$165.75	$165.80
Purchase #4	$122.42	6.558%	$130.4483	$130.45	$130.45	$130.40
Purchase #5	$224.54	7.712%	$241.8565	$241.86	$241.85	$241.90
Purchase #6	$126.45	12.616%	$142.4029	$142.40	$142.40	$142.40
Purchase #7	$52.86	8.700%	$57.4588	$57.46	$57.45	$57.50
7 purchase totals =	$903.03		$976.9148	$976.93	$976.90	$976.90