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	$30.53	12.357%	$34.3026	$34.30	$34.30	$34.30
Purchase #2	$224.25	11.253%	$249.4849	$249.48	$249.50	$249.50
Purchase #3	$59.62	10.395%	$65.8175	$65.82	$65.80	$65.80
Purchase #4	$161.52	6.542%	$172.0866	$172.09	$172.10	$172.10
Purchase #5	$99.42	10.355%	$109.7149	$109.71	$109.70	$109.70
Purchase #6	$245.81	4.375%	$256.5642	$256.56	$256.55	$256.60
Purchase #7	$208.64	7.594%	$224.4841	$224.48	$224.50	$224.50
7 purchase totals =	$1,029.79		$1,112.4548	$1,112.44	$1,112.45	$1,112.50