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	$65.28	9.570%	$71.5273	$71.53	$71.55	$71.50
Purchase #2	$182.98	3.368%	$189.1428	$189.14	$189.15	$189.10
Purchase #3	$65.64	6.643%	$70.0005	$70.00	$70.00	$70.00
Purchase #4	$40.74	10.529%	$45.0295	$45.03	$45.05	$45.00
Purchase #5	$30.55	6.439%	$32.5171	$32.52	$32.50	$32.50
Purchase #6	$114.66	11.609%	$127.9709	$127.97	$127.95	$128.00
Purchase #7	$32.74	5.266%	$34.4641	$34.46	$34.45	$34.50
7 purchase totals =	$532.59		$570.6522	$570.65	$570.65	$570.60