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	$24.71	6.704%	$26.3666	$26.37	$26.35	$26.40
Purchase #2	$204.38	7.399%	$219.5021	$219.50	$219.50	$219.50
Purchase #3	$8.29	5.261%	$8.7261	$8.73	$8.75	$8.70
Purchase #4	$29.50	10.250%	$32.5238	$32.52	$32.50	$32.50
Purchase #5	$73.89	13.424%	$83.809	$83.81	$83.80	$83.80
Purchase #6	$189.66	5.790%	$200.6413	$200.64	$200.65	$200.60
Purchase #7	$83.53	8.735%	$90.8263	$90.83	$90.85	$90.80
7 purchase totals =	$613.96		$662.3952	$662.40	$662.40	$662.30