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	$230.93	10.482%	$255.1361	$255.14	$255.15	$255.10
Purchase #2	$199.40	6.311%	$211.9841	$211.98	$212.00	$212.00
Purchase #3	$173.88	5.389%	$183.2504	$183.25	$183.25	$183.30
Purchase #4	$237.40	7.569%	$255.3688	$255.37	$255.35	$255.40
Purchase #5	$177.39	12.502%	$199.5673	$199.57	$199.55	$199.60
Purchase #6	$116.84	11.668%	$130.4729	$130.47	$130.45	$130.50
Purchase #7	$152.46	10.774%	$168.886	$168.89	$168.90	$168.90
7 purchase totals =	$1,288.30		$1,404.6656	$1,404.67	$1,404.65	$1,404.80