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	$152.96	5.645%	$161.5946	$161.59	$161.60	$161.60
Purchase #2	$149.87	4.315%	$156.3369	$156.34	$156.35	$156.30
Purchase #3	$80.51	13.557%	$91.4247	$91.42	$91.40	$91.40
Purchase #4	$249.67	7.449%	$268.2679	$268.27	$268.25	$268.30
Purchase #5	$161.72	5.372%	$170.4076	$170.41	$170.40	$170.40
Purchase #6	$134.78	7.500%	$144.8885	$144.89	$144.90	$144.90
Purchase #7	$116.53	12.189%	$130.7338	$130.73	$130.75	$130.70
7 purchase totals =	$1,046.04		$1,123.6540	$1,123.65	$1,123.65	$1,123.60