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	$77.33	7.396%	$83.0493	$83.05	$83.05	$83.00
Purchase #2	$132.55	6.478%	$141.1366	$141.14	$141.15	$141.10
Purchase #3	$114.79	5.815%	$121.465	$121.47	$121.45	$121.50
Purchase #4	$78.34	13.321%	$88.7757	$88.78	$88.80	$88.80
Purchase #5	$223.48	3.256%	$230.7565	$230.76	$230.75	$230.80
Purchase #6	$137.64	9.315%	$150.4612	$150.46	$150.45	$150.50
Purchase #7	$209.54	4.483%	$218.9337	$218.93	$218.95	$218.90
7 purchase totals =	$973.67		$1,034.5780	$1,034.59	$1,034.60	$1,034.60