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	$99.49	3.526%	$102.998	$103.00	$103.00	$103.00
Purchase #2	$59.89	5.733%	$63.3235	$63.32	$63.30	$63.30
Purchase #3	$150.39	12.181%	$168.709	$168.71	$168.70	$168.70
Purchase #4	$70.41	11.590%	$78.5705	$78.57	$78.55	$78.60
Purchase #5	$242.48	5.612%	$256.088	$256.09	$256.10	$256.10
Purchase #6	$53.65	13.663%	$60.9802	$60.98	$61.00	$61.00
Purchase #7	$74.99	7.839%	$80.8685	$80.87	$80.85	$80.90
7 purchase totals =	$751.30		$811.5377	$811.54	$811.50	$811.60