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	$40.80	3.225%	$42.1158	$42.12	$42.10	$42.10
Purchase #2	$55.97	5.483%	$59.0388	$59.04	$59.05	$59.00
Purchase #3	$207.37	11.470%	$231.1553	$231.16	$231.15	$231.20
Purchase #4	$21.61	9.365%	$23.6338	$23.63	$23.65	$23.60
Purchase #5	$167.71	4.253%	$174.8427	$174.84	$174.85	$174.80
Purchase #6	$199.40	11.388%	$222.1077	$222.11	$222.10	$222.10
Purchase #7	$132.39	6.588%	$141.1119	$141.11	$141.10	$141.10
7 purchase totals =	$825.25		$894.0060	$894.01	$894.00	$893.90