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	$100.63	4.183%	$104.8394	$104.84	$104.85	$104.80
Purchase #2	$73.56	4.137%	$76.6032	$76.60	$76.60	$76.60
Purchase #3	$221.77	11.443%	$247.1471	$247.15	$247.15	$247.10
Purchase #4	$123.98	5.800%	$131.1708	$131.17	$131.15	$131.20
Purchase #5	$35.95	4.559%	$37.589	$37.59	$37.60	$37.60
Purchase #6	$237.70	13.619%	$270.0724	$270.07	$270.05	$270.10
Purchase #7	$246.97	13.566%	$280.474	$280.47	$280.45	$280.50
7 purchase totals =	$1,040.56		$1,147.8959	$1,147.89	$1,147.85	$1,147.90