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	$131.86	4.547%	$137.8557	$137.86	$137.85	$137.90
Purchase #2	$204.77	12.793%	$230.9662	$230.97	$230.95	$231.00
Purchase #3	$235.26	3.635%	$243.8117	$243.81	$243.80	$243.80
Purchase #4	$111.82	5.687%	$118.1792	$118.18	$118.20	$118.20
Purchase #5	$158.55	12.489%	$178.3513	$178.35	$178.35	$178.40
Purchase #6	$99.66	4.821%	$104.4646	$104.46	$104.45	$104.50
Purchase #7	$130.56	9.398%	$142.83	$142.83	$142.85	$142.80
7 purchase totals =	$1,072.48		$1,156.4587	$1,156.46	$1,156.45	$1,156.60