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	$190.29	4.297%	$198.4668	$198.47	$198.45	$198.50
Purchase #2	$248.28	6.470%	$264.3437	$264.34	$264.35	$264.30
Purchase #3	$54.47	13.119%	$61.6159	$61.62	$61.60	$61.60
Purchase #4	$215.47	9.299%	$235.5066	$235.51	$235.50	$235.50
Purchase #5	$190.86	4.588%	$199.6167	$199.62	$199.60	$199.60
Purchase #6	$92.54	3.267%	$95.5633	$95.56	$95.55	$95.60
Purchase #7	$102.66	10.466%	$113.4044	$113.40	$113.40	$113.40
7 purchase totals =	$1,094.57		$1,168.5174	$1,168.52	$1,168.45	$1,168.50