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	$210.64	4.154%	$219.39	$219.39	$219.40	$219.40
Purchase #2	$199.29	13.138%	$225.4727	$225.47	$225.45	$225.50
Purchase #3	$133.33	12.641%	$150.1842	$150.18	$150.20	$150.20
Purchase #4	$64.31	10.130%	$70.8246	$70.82	$70.80	$70.80
Purchase #5	$204.86	3.274%	$211.5671	$211.57	$211.55	$211.60
Purchase #6	$189.68	3.352%	$196.0381	$196.04	$196.05	$196.00
Purchase #7	$140.71	6.654%	$150.0728	$150.07	$150.05	$150.10
7 purchase totals =	$1,142.82		$1,223.5495	$1,223.54	$1,223.50	$1,223.60