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	$250.47	10.420%	$276.569	$276.57	$276.55	$276.60
Purchase #2	$161.72	10.743%	$179.0936	$179.09	$179.10	$179.10
Purchase #3	$55.38	7.293%	$59.4189	$59.42	$59.40	$59.40
Purchase #4	$227.47	6.770%	$242.8697	$242.87	$242.85	$242.90
Purchase #5	$43.95	4.405%	$45.886	$45.89	$45.90	$45.90
Purchase #6	$56.56	6.872%	$60.4468	$60.45	$60.45	$60.40
Purchase #7	$210.71	13.308%	$238.7513	$238.75	$238.75	$238.80
7 purchase totals =	$1,006.26		$1,103.0353	$1,103.04	$1,103.00	$1,103.10