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	$238.46	8.500%	$258.7291	$258.73	$258.75	$258.70
Purchase #2	$70.41	4.662%	$73.6925	$73.69	$73.70	$73.70
Purchase #3	$127.29	4.113%	$132.5254	$132.53	$132.55	$132.50
Purchase #4	$112.97	9.114%	$123.2661	$123.27	$123.25	$123.30
Purchase #5	$162.37	10.199%	$178.9301	$178.93	$178.95	$178.90
Purchase #6	$223.59	7.141%	$239.5566	$239.56	$239.55	$239.60
Purchase #7	$110.25	5.443%	$116.2509	$116.25	$116.25	$116.30
7 purchase totals =	$1,045.34		$1,122.9507	$1,122.96	$1,123.00	$1,123.00