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	$42.75	7.203%	$45.8293	$45.83	$45.85	$45.80
Purchase #2	$53.95	9.666%	$59.1648	$59.16	$59.15	$59.20
Purchase #3	$206.80	9.410%	$226.2599	$226.26	$226.25	$226.30
Purchase #4	$193.83	8.613%	$210.5246	$210.52	$210.50	$210.50
Purchase #5	$52.51	13.764%	$59.7375	$59.74	$59.75	$59.70
Purchase #6	$214.99	5.603%	$227.0359	$227.04	$227.05	$227.00
Purchase #7	$178.65	12.197%	$200.4399	$200.44	$200.45	$200.40
7 purchase totals =	$943.48		$1,028.9919	$1,028.99	$1,029.00	$1,028.90