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	$237.28	5.424%	$250.1501	$250.15	$250.15	$250.20
Purchase #2	$211.80	12.633%	$238.5567	$238.56	$238.55	$238.60
Purchase #3	$187.34	6.825%	$200.126	$200.13	$200.15	$200.10
Purchase #4	$105.96	6.175%	$112.503	$112.50	$112.50	$112.50
Purchase #5	$243.50	5.272%	$256.3373	$256.34	$256.35	$256.30
Purchase #6	$104.26	7.239%	$111.8074	$111.81	$111.80	$111.80
Purchase #7	$121.65	5.602%	$128.4648	$128.46	$128.45	$128.50
7 purchase totals =	$1,211.79		$1,297.9453	$1,297.95	$1,297.95	$1,298.00