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	$72.62	5.769%	$76.8094	$76.81	$76.80	$76.80
Purchase #2	$197.59	12.495%	$222.2789	$222.28	$222.30	$222.30
Purchase #3	$172.39	11.511%	$192.2338	$192.23	$192.25	$192.20
Purchase #4	$124.96	12.474%	$140.5475	$140.55	$140.55	$140.50
Purchase #5	$129.85	3.314%	$134.1532	$134.15	$134.15	$134.20
Purchase #6	$77.28	6.219%	$82.086	$82.09	$82.10	$82.10
Purchase #7	$20.42	4.446%	$21.3279	$21.33	$21.35	$21.30
7 purchase totals =	$795.11		$869.4367	$869.44	$869.50	$869.40