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	$42.71	11.689%	$47.7024	$47.70	$47.70	$47.70
Purchase #2	$164.82	12.433%	$185.3121	$185.31	$185.30	$185.30
Purchase #3	$118.75	12.723%	$133.8586	$133.86	$133.85	$133.90
Purchase #4	$83.31	12.637%	$93.8379	$93.84	$93.85	$93.80
Purchase #5	$229.47	5.358%	$241.765	$241.77	$241.75	$241.80
Purchase #6	$37.48	13.184%	$42.4214	$42.42	$42.40	$42.40
Purchase #7	$181.62	10.195%	$200.1362	$200.14	$200.15	$200.10
7 purchase totals =	$858.16		$945.0336	$945.04	$945.00	$945.00