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	$54.58	8.766%	$59.3645	$59.36	$59.35	$59.40
Purchase #2	$238.31	7.367%	$255.8663	$255.87	$255.85	$255.90
Purchase #3	$83.55	9.424%	$91.4238	$91.42	$91.40	$91.40
Purchase #4	$93.50	8.460%	$101.4101	$101.41	$101.40	$101.40
Purchase #5	$152.70	7.717%	$164.4839	$164.48	$164.50	$164.50
Purchase #6	$195.40	8.215%	$211.4521	$211.45	$211.45	$211.50
Purchase #7	$216.86	3.778%	$225.053	$225.05	$225.05	$225.10
7 purchase totals =	$1,034.90		$1,109.0537	$1,109.04	$1,109.00	$1,109.20