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	$193.54	6.521%	$206.1607	$206.16	$206.15	$206.20
Purchase #2	$68.70	5.345%	$72.372	$72.37	$72.35	$72.40
Purchase #3	$104.77	7.321%	$112.4402	$112.44	$112.45	$112.40
Purchase #4	$37.85	7.665%	$40.7512	$40.75	$40.75	$40.80
Purchase #5	$143.32	11.299%	$159.5137	$159.51	$159.50	$159.50
Purchase #6	$231.89	13.640%	$263.5198	$263.52	$263.50	$263.50
Purchase #7	$73.86	9.821%	$81.1138	$81.11	$81.10	$81.10
7 purchase totals =	$853.93		$935.8714	$935.86	$935.80	$935.90