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	$201.39	4.391%	$210.233	$210.23	$210.25	$210.20
Purchase #2	$211.39	4.789%	$221.5135	$221.51	$221.50	$221.50
Purchase #3	$47.53	13.399%	$53.8985	$53.90	$53.90	$53.90
Purchase #4	$14.55	5.863%	$15.4031	$15.40	$15.40	$15.40
Purchase #5	$227.36	9.203%	$248.2839	$248.28	$248.30	$248.30
Purchase #6	$35.88	5.584%	$37.8835	$37.88	$37.90	$37.90
Purchase #7	$81.31	8.688%	$88.3742	$88.37	$88.35	$88.40
7 purchase totals =	$819.41		$875.5897	$875.57	$875.60	$875.60