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	$80.59	7.301%	$86.4739	$86.47	$86.45	$86.50
Purchase #2	$250.35	5.833%	$264.9529	$264.95	$264.95	$265.00
Purchase #3	$91.83	13.432%	$104.1646	$104.16	$104.15	$104.20
Purchase #4	$245.33	4.590%	$256.5906	$256.59	$256.60	$256.60
Purchase #5	$119.95	9.263%	$131.061	$131.06	$131.05	$131.10
Purchase #6	$249.34	6.128%	$264.6196	$264.62	$264.60	$264.60
Purchase #7	$139.65	11.604%	$155.855	$155.86	$155.85	$155.90
7 purchase totals =	$1,177.04		$1,263.7176	$1,263.71	$1,263.65	$1,263.90