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	$62.59	3.113%	$64.5384	$64.54	$64.55	$64.50
Purchase #2	$177.71	4.222%	$185.2129	$185.21	$185.20	$185.20
Purchase #3	$52.38	5.165%	$55.0854	$55.09	$55.10	$55.10
Purchase #4	$111.85	11.572%	$124.7933	$124.79	$124.80	$124.80
Purchase #5	$138.79	9.490%	$151.9612	$151.96	$151.95	$152.00
Purchase #6	$39.61	13.729%	$45.0481	$45.05	$45.05	$45.00
Purchase #7	$118.33	11.196%	$131.5782	$131.58	$131.60	$131.60
7 purchase totals =	$701.26		$758.2175	$758.22	$758.25	$758.20