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	$195.59	9.811%	$214.7793	$214.78	$214.80	$214.80
Purchase #2	$71.68	9.567%	$78.5376	$78.54	$78.55	$78.50
Purchase #3	$43.45	4.140%	$45.2488	$45.25	$45.25	$45.20
Purchase #4	$13.49	3.103%	$13.9086	$13.91	$13.90	$13.90
Purchase #5	$5.81	3.599%	$6.0191	$6.02	$6.00	$6.00
Purchase #6	$136.98	7.160%	$146.7878	$146.79	$146.80	$146.80
Purchase #7	$119.33	6.398%	$126.9647	$126.96	$126.95	$127.00
7 purchase totals =	$586.33		$632.2459	$632.25	$632.25	$632.20