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	$173.66	8.558%	$188.5218	$188.52	$188.50	$188.50
Purchase #2	$212.46	13.113%	$240.3199	$240.32	$240.30	$240.30
Purchase #3	$123.82	5.719%	$130.9013	$130.90	$130.90	$130.90
Purchase #4	$199.73	9.418%	$218.5406	$218.54	$218.55	$218.50
Purchase #5	$173.70	10.832%	$192.5152	$192.52	$192.50	$192.50
Purchase #6	$55.29	12.647%	$62.2825	$62.28	$62.30	$62.30
Purchase #7	$114.96	4.845%	$120.5298	$120.53	$120.55	$120.50
7 purchase totals =	$1,053.62		$1,153.6111	$1,153.61	$1,153.60	$1,153.50