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	$105.58	5.350%	$111.2285	$111.23	$111.25	$111.20
Purchase #2	$54.77	10.406%	$60.4694	$60.47	$60.45	$60.50
Purchase #3	$227.86	9.197%	$248.8163	$248.82	$248.80	$248.80
Purchase #4	$108.71	10.840%	$120.4942	$120.49	$120.50	$120.50
Purchase #5	$203.40	4.701%	$212.9618	$212.96	$212.95	$213.00
Purchase #6	$213.82	13.774%	$243.2716	$243.27	$243.25	$243.30
Purchase #7	$16.38	12.232%	$18.3836	$18.38	$18.40	$18.40
7 purchase totals =	$930.52		$1,015.6254	$1,015.62	$1,015.60	$1,015.70