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	$123.65	5.467%	$130.4099	$130.41	$130.40	$130.40
Purchase #2	$200.39	4.591%	$209.5899	$209.59	$209.60	$209.60
Purchase #3	$21.98	7.454%	$23.6184	$23.62	$23.60	$23.60
Purchase #4	$178.72	6.503%	$190.3422	$190.34	$190.35	$190.30
Purchase #5	$169.54	3.709%	$175.8282	$175.83	$175.85	$175.80
Purchase #6	$143.41	4.863%	$150.384	$150.38	$150.40	$150.40
Purchase #7	$152.97	11.233%	$170.1531	$170.15	$170.15	$170.20
7 purchase totals =	$990.66		$1,050.3257	$1,050.32	$1,050.35	$1,050.30