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	$173.57	4.307%	$181.0457	$181.05	$181.05	$181.00
Purchase #2	$73.56	12.213%	$82.5439	$82.54	$82.55	$82.50
Purchase #3	$159.71	13.633%	$181.4833	$181.48	$181.50	$181.50
Purchase #4	$247.71	10.403%	$273.4793	$273.48	$273.50	$273.50
Purchase #5	$22.31	10.144%	$24.5731	$24.57	$24.55	$24.60
Purchase #6	$35.32	4.335%	$36.8511	$36.85	$36.85	$36.90
Purchase #7	$247.91	13.239%	$280.7308	$280.73	$280.75	$280.70
7 purchase totals =	$960.09		$1,060.7072	$1,060.70	$1,060.75	$1,060.70