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	$161.82	8.724%	$175.9372	$175.94	$175.95	$175.90
Purchase #2	$72.96	7.736%	$78.6042	$78.60	$78.60	$78.60
Purchase #3	$244.92	11.786%	$273.7863	$273.79	$273.80	$273.80
Purchase #4	$21.25	5.747%	$22.4712	$22.47	$22.45	$22.50
Purchase #5	$48.58	7.303%	$52.1278	$52.13	$52.15	$52.10
Purchase #6	$140.72	6.859%	$150.372	$150.37	$150.35	$150.40
Purchase #7	$105.97	12.411%	$119.1219	$119.12	$119.10	$119.10
7 purchase totals =	$796.22		$872.4206	$872.42	$872.40	$872.40