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	$115.50	3.610%	$119.6696	$119.67	$119.65	$119.70
Purchase #2	$201.40	12.102%	$225.7734	$225.77	$225.75	$225.80
Purchase #3	$174.44	3.673%	$180.8472	$180.85	$180.85	$180.80
Purchase #4	$85.57	5.780%	$90.5159	$90.52	$90.50	$90.50
Purchase #5	$87.47	10.176%	$96.3709	$96.37	$96.35	$96.40
Purchase #6	$134.84	8.176%	$145.8645	$145.86	$145.85	$145.90
Purchase #7	$32.66	8.288%	$35.3669	$35.37	$35.35	$35.40
7 purchase totals =	$831.88		$894.4084	$894.41	$894.30	$894.50