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	$148.54	4.576%	$155.3372	$155.34	$155.35	$155.30
Purchase #2	$6.70	7.368%	$7.1937	$7.19	$7.20	$7.20
Purchase #3	$246.75	13.820%	$280.8509	$280.85	$280.85	$280.90
Purchase #4	$17.54	5.117%	$18.4375	$18.44	$18.45	$18.40
Purchase #5	$246.95	3.452%	$255.4747	$255.47	$255.45	$255.50
Purchase #6	$209.40	3.311%	$216.3332	$216.33	$216.35	$216.30
Purchase #7	$94.92	10.159%	$104.5629	$104.56	$104.55	$104.60
7 purchase totals =	$970.80		$1,038.1901	$1,038.18	$1,038.20	$1,038.20