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	$52.67	12.871%	$59.4492	$59.45	$59.45	$59.40
Purchase #2	$164.99	6.642%	$175.9486	$175.95	$175.95	$175.90
Purchase #3	$67.86	5.281%	$71.4437	$71.44	$71.45	$71.40
Purchase #4	$209.57	13.116%	$237.0572	$237.06	$237.05	$237.10
Purchase #5	$104.56	12.427%	$117.5537	$117.55	$117.55	$117.60
Purchase #6	$35.85	4.675%	$37.526	$37.53	$37.55	$37.50
Purchase #7	$6.29	5.313%	$6.6242	$6.62	$6.60	$6.60
7 purchase totals =	$641.79		$705.6026	$705.60	$705.60	$705.50