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	$165.43	11.637%	$184.6811	$184.68	$184.70	$184.70
Purchase #2	$178.86	11.153%	$198.8083	$198.81	$198.80	$198.80
Purchase #3	$37.94	5.465%	$40.0134	$40.01	$40.00	$40.00
Purchase #4	$93.70	11.102%	$104.1026	$104.10	$104.10	$104.10
Purchase #5	$131.40	10.131%	$144.7121	$144.71	$144.70	$144.70
Purchase #6	$72.98	6.123%	$77.4486	$77.45	$77.45	$77.40
Purchase #7	$245.46	3.475%	$253.9897	$253.99	$254.00	$254.00
7 purchase totals =	$925.77		$1,003.7558	$1,003.75	$1,003.75	$1,003.70