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	$232.37	6.753%	$248.0619	$248.06	$248.05	$248.10
Purchase #2	$157.76	9.344%	$172.5011	$172.50	$172.50	$172.50
Purchase #3	$65.53	11.114%	$72.813	$72.81	$72.80	$72.80
Purchase #4	$91.46	13.281%	$103.6068	$103.61	$103.60	$103.60
Purchase #5	$54.87	7.605%	$59.0429	$59.04	$59.05	$59.00
Purchase #6	$62.76	10.507%	$69.3542	$69.35	$69.35	$69.40
Purchase #7	$92.33	10.598%	$102.1151	$102.12	$102.10	$102.10
7 purchase totals =	$757.08		$827.4950	$827.49	$827.45	$827.50