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	$196.61	13.188%	$222.5389	$222.54	$222.55	$222.50
Purchase #2	$93.46	12.108%	$104.7761	$104.78	$104.80	$104.80
Purchase #3	$103.54	13.770%	$117.7975	$117.80	$117.80	$117.80
Purchase #4	$167.89	10.503%	$185.5235	$185.52	$185.50	$185.50
Purchase #5	$67.66	11.675%	$75.5593	$75.56	$75.55	$75.60
Purchase #6	$244.97	13.493%	$278.0238	$278.02	$278.00	$278.00
Purchase #7	$117.92	7.397%	$126.6425	$126.64	$126.65	$126.60
7 purchase totals =	$992.05		$1,110.8616	$1,110.86	$1,110.85	$1,110.80