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	$191.82	12.132%	$215.0916	$215.09	$215.10	$215.10
Purchase #2	$127.75	13.362%	$144.82	$144.82	$144.80	$144.80
Purchase #3	$197.56	7.723%	$212.8176	$212.82	$212.80	$212.80
Purchase #4	$249.83	13.489%	$283.5296	$283.53	$283.55	$283.50
Purchase #5	$201.81	8.137%	$218.2313	$218.23	$218.25	$218.20
Purchase #6	$7.43	4.277%	$7.7478	$7.75	$7.75	$7.70
Purchase #7	$70.93	10.487%	$78.3684	$78.37	$78.35	$78.40
7 purchase totals =	$1,047.13		$1,160.6063	$1,160.61	$1,160.60	$1,160.50