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	$185.42	5.618%	$195.8369	$195.84	$195.85	$195.80
Purchase #2	$73.72	10.130%	$81.1878	$81.19	$81.20	$81.20
Purchase #3	$43.48	4.714%	$45.5296	$45.53	$45.55	$45.50
Purchase #4	$206.92	10.601%	$228.8556	$228.86	$228.85	$228.90
Purchase #5	$194.84	4.561%	$203.7267	$203.73	$203.75	$203.70
Purchase #6	$55.33	6.833%	$59.1107	$59.11	$59.10	$59.10
Purchase #7	$170.64	11.735%	$190.6646	$190.66	$190.65	$190.70
7 purchase totals =	$930.35		$1,004.9119	$1,004.92	$1,004.95	$1,004.90