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	$190.52	8.248%	$206.2341	$206.23	$206.25	$206.20
Purchase #2	$192.97	9.481%	$211.2655	$211.27	$211.25	$211.30
Purchase #3	$69.93	3.114%	$72.1076	$72.11	$72.10	$72.10
Purchase #4	$105.76	4.662%	$110.6905	$110.69	$110.70	$110.70
Purchase #5	$56.60	4.699%	$59.2596	$59.26	$59.25	$59.30
Purchase #6	$160.74	3.638%	$166.5877	$166.59	$166.60	$166.60
Purchase #7	$233.73	4.863%	$245.0963	$245.10	$245.10	$245.10
7 purchase totals =	$1,010.25		$1,071.2413	$1,071.25	$1,071.25	$1,071.30