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	$223.55	4.854%	$234.4011	$234.40	$234.40	$234.40
Purchase #2	$69.48	11.870%	$77.7273	$77.73	$77.75	$77.70
Purchase #3	$176.60	7.697%	$190.1929	$190.19	$190.20	$190.20
Purchase #4	$184.51	5.844%	$195.2928	$195.29	$195.30	$195.30
Purchase #5	$231.29	5.240%	$243.4096	$243.41	$243.40	$243.40
Purchase #6	$37.28	3.541%	$38.6001	$38.60	$38.60	$38.60
Purchase #7	$105.61	10.318%	$116.5068	$116.51	$116.50	$116.50
7 purchase totals =	$1,028.32		$1,096.1306	$1,096.13	$1,096.15	$1,096.10