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	$188.96	10.113%	$208.0695	$208.07	$208.05	$208.10
Purchase #2	$18.93	13.586%	$21.5018	$21.50	$21.50	$21.50
Purchase #3	$186.95	7.279%	$200.5581	$200.56	$200.55	$200.60
Purchase #4	$181.67	8.342%	$196.8249	$196.82	$196.80	$196.80
Purchase #5	$33.50	9.488%	$36.6785	$36.68	$36.70	$36.70
Purchase #6	$48.27	10.298%	$53.2408	$53.24	$53.25	$53.20
Purchase #7	$231.38	4.326%	$241.3895	$241.39	$241.40	$241.40
7 purchase totals =	$889.66		$958.2631	$958.26	$958.25	$958.30