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	$42.37	7.674%	$45.6215	$45.62	$45.60	$45.60
Purchase #2	$247.73	9.856%	$272.1463	$272.15	$272.15	$272.10
Purchase #3	$212.71	8.750%	$231.3221	$231.32	$231.30	$231.30
Purchase #4	$33.82	5.113%	$35.5492	$35.55	$35.55	$35.50
Purchase #5	$209.52	6.695%	$223.5474	$223.55	$223.55	$223.50
Purchase #6	$10.53	5.752%	$11.1357	$11.14	$11.15	$11.10
Purchase #7	$192.75	9.470%	$211.0034	$211.00	$211.00	$211.00
7 purchase totals =	$949.43		$1,030.3256	$1,030.33	$1,030.30	$1,030.10