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	$198.56	12.245%	$222.8737	$222.87	$222.85	$222.90
Purchase #2	$15.84	10.599%	$17.5189	$17.52	$17.50	$17.50
Purchase #3	$218.31	12.361%	$245.2953	$245.30	$245.30	$245.30
Purchase #4	$67.60	8.585%	$73.4035	$73.40	$73.40	$73.40
Purchase #5	$150.59	9.772%	$165.3057	$165.31	$165.30	$165.30
Purchase #6	$120.27	3.502%	$124.4819	$124.48	$124.50	$124.50
Purchase #7	$199.74	6.425%	$212.5733	$212.57	$212.55	$212.60
7 purchase totals =	$970.91		$1,061.4523	$1,061.45	$1,061.40	$1,061.50