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	$72.78	13.252%	$82.4248	$82.42	$82.40	$82.40
Purchase #2	$188.34	5.609%	$198.904	$198.90	$198.90	$198.90
Purchase #3	$132.47	3.119%	$136.6017	$136.60	$136.60	$136.60
Purchase #4	$215.74	6.457%	$229.6703	$229.67	$229.65	$229.70
Purchase #5	$235.93	3.750%	$244.7774	$244.78	$244.80	$244.80
Purchase #6	$96.96	6.578%	$103.338	$103.34	$103.35	$103.30
Purchase #7	$51.39	13.777%	$58.47	$58.47	$58.45	$58.50
7 purchase totals =	$993.61		$1,054.1862	$1,054.18	$1,054.15	$1,054.20