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	$203.80	4.810%	$213.6028	$213.60	$213.60	$213.60
Purchase #2	$53.78	7.252%	$57.6801	$57.68	$57.70	$57.70
Purchase #3	$111.96	7.462%	$120.3145	$120.31	$120.30	$120.30
Purchase #4	$135.93	4.772%	$142.4166	$142.42	$142.40	$142.40
Purchase #5	$247.34	10.167%	$272.4871	$272.49	$272.50	$272.50
Purchase #6	$247.65	4.357%	$258.4401	$258.44	$258.45	$258.40
Purchase #7	$77.29	10.783%	$85.6242	$85.62	$85.60	$85.60
7 purchase totals =	$1,077.75		$1,150.5654	$1,150.56	$1,150.55	$1,150.50