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	$179.84	5.111%	$189.0316	$189.03	$189.05	$189.00
Purchase #2	$116.91	3.454%	$120.9481	$120.95	$120.95	$120.90
Purchase #3	$212.75	9.492%	$232.9442	$232.94	$232.95	$232.90
Purchase #4	$113.93	12.144%	$127.7657	$127.77	$127.75	$127.80
Purchase #5	$222.63	4.818%	$233.3563	$233.36	$233.35	$233.40
Purchase #6	$114.52	8.166%	$123.8717	$123.87	$123.85	$123.90
Purchase #7	$88.45	8.193%	$95.6967	$95.70	$95.70	$95.70
7 purchase totals =	$1,049.03		$1,123.6143	$1,123.62	$1,123.60	$1,123.60