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	$192.77	10.727%	$213.4484	$213.45	$213.45	$213.40
Purchase #2	$96.75	4.455%	$101.0602	$101.06	$101.05	$101.10
Purchase #3	$193.96	7.350%	$208.2161	$208.22	$208.20	$208.20
Purchase #4	$123.89	12.622%	$139.5274	$139.53	$139.55	$139.50
Purchase #5	$35.30	7.327%	$37.8864	$37.89	$37.90	$37.90
Purchase #6	$223.40	6.315%	$237.5077	$237.51	$237.50	$237.50
Purchase #7	$56.96	3.849%	$59.1524	$59.15	$59.15	$59.20
7 purchase totals =	$923.03		$996.7986	$996.81	$996.80	$996.80