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	$15.94	4.209%	$16.6109	$16.61	$16.60	$16.60
Purchase #2	$174.60	9.399%	$191.0107	$191.01	$191.00	$191.00
Purchase #3	$8.48	4.255%	$8.8408	$8.84	$8.85	$8.80
Purchase #4	$61.47	6.568%	$65.5073	$65.51	$65.50	$65.50
Purchase #5	$111.57	10.305%	$123.0673	$123.07	$123.05	$123.10
Purchase #6	$41.46	13.386%	$47.0098	$47.01	$47.00	$47.00
Purchase #7	$38.98	9.114%	$42.5326	$42.53	$42.55	$42.50
7 purchase totals =	$452.50		$494.5794	$494.58	$494.55	$494.50