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	$156.60	7.772%	$168.771	$168.77	$168.75	$168.80
Purchase #2	$125.47	8.662%	$136.3382	$136.34	$136.35	$136.30
Purchase #3	$231.57	9.869%	$254.4236	$254.42	$254.40	$254.40
Purchase #4	$97.57	9.436%	$106.7767	$106.78	$106.80	$106.80
Purchase #5	$82.28	3.558%	$85.2075	$85.21	$85.20	$85.20
Purchase #6	$244.66	12.401%	$275.0003	$275.00	$275.00	$275.00
Purchase #7	$172.88	10.419%	$190.8924	$190.89	$190.90	$190.90
7 purchase totals =	$1,111.03		$1,217.4097	$1,217.41	$1,217.40	$1,217.40