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	$78.34	13.328%	$88.7812	$88.78	$88.80	$88.80
Purchase #2	$78.74	4.347%	$82.1628	$82.16	$82.15	$82.20
Purchase #3	$27.90	3.739%	$28.9432	$28.94	$28.95	$28.90
Purchase #4	$171.97	13.735%	$195.5901	$195.59	$195.60	$195.60
Purchase #5	$101.83	10.779%	$112.8063	$112.81	$112.80	$112.80
Purchase #6	$200.77	13.385%	$227.6431	$227.64	$227.65	$227.60
Purchase #7	$124.89	11.576%	$139.3473	$139.35	$139.35	$139.30
7 purchase totals =	$784.44		$875.2740	$875.27	$875.30	$875.20