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	$166.25	3.722%	$172.4378	$172.44	$172.45	$172.40
Purchase #2	$26.83	6.197%	$28.4927	$28.49	$28.50	$28.50
Purchase #3	$143.71	5.451%	$151.5436	$151.54	$151.55	$151.50
Purchase #4	$164.25	6.625%	$175.1316	$175.13	$175.15	$175.10
Purchase #5	$250.37	9.371%	$273.8322	$273.83	$273.85	$273.80
Purchase #6	$92.66	11.673%	$103.4762	$103.48	$103.50	$103.50
Purchase #7	$214.48	8.566%	$232.8524	$232.85	$232.85	$232.90
7 purchase totals =	$1,058.55		$1,137.7665	$1,137.76	$1,137.85	$1,137.70