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	$148.82	4.648%	$155.7372	$155.74	$155.75	$155.70
Purchase #2	$64.70	6.872%	$69.1462	$69.15	$69.15	$69.10
Purchase #3	$56.77	4.534%	$59.344	$59.34	$59.35	$59.30
Purchase #4	$245.46	13.265%	$278.0203	$278.02	$278.00	$278.00
Purchase #5	$189.79	4.563%	$198.4501	$198.45	$198.45	$198.50
Purchase #6	$77.29	8.161%	$83.5976	$83.60	$83.60	$83.60
Purchase #7	$243.52	5.245%	$256.2926	$256.29	$256.30	$256.30
7 purchase totals =	$1,026.35		$1,100.5880	$1,100.59	$1,100.60	$1,100.50