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	$65.31	9.806%	$71.7143	$71.71	$71.70	$71.70
Purchase #2	$168.84	6.525%	$179.8568	$179.86	$179.85	$179.90
Purchase #3	$171.28	8.575%	$185.9673	$185.97	$185.95	$186.00
Purchase #4	$70.54	4.565%	$73.7602	$73.76	$73.75	$73.80
Purchase #5	$112.70	9.462%	$123.3637	$123.36	$123.35	$123.40
Purchase #6	$133.33	9.840%	$146.4497	$146.45	$146.45	$146.40
Purchase #7	$37.94	13.822%	$43.1841	$43.18	$43.20	$43.20
7 purchase totals =	$759.94		$824.2961	$824.29	$824.25	$824.40