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	$121.36	7.829%	$130.8613	$130.86	$130.85	$130.90
Purchase #2	$120.34	11.365%	$134.0166	$134.02	$134.00	$134.00
Purchase #3	$100.66	10.302%	$111.03	$111.03	$111.05	$111.00
Purchase #4	$40.54	3.724%	$42.0497	$42.05	$42.05	$42.00
Purchase #5	$179.79	11.595%	$200.6367	$200.64	$200.65	$200.60
Purchase #6	$70.95	5.554%	$74.8906	$74.89	$74.90	$74.90
Purchase #7	$32.61	6.127%	$34.608	$34.61	$34.60	$34.60
7 purchase totals =	$666.25		$728.0929	$728.10	$728.10	$728.00