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	$243.93	8.253%	$264.0615	$264.06	$264.05	$264.10
Purchase #2	$220.92	4.481%	$230.8194	$230.82	$230.80	$230.80
Purchase #3	$14.33	3.690%	$14.8588	$14.86	$14.85	$14.90
Purchase #4	$172.42	7.522%	$185.3894	$185.39	$185.40	$185.40
Purchase #5	$67.99	4.493%	$71.0448	$71.04	$71.05	$71.00
Purchase #6	$126.31	8.830%	$137.4632	$137.46	$137.45	$137.50
Purchase #7	$130.32	10.668%	$144.2225	$144.22	$144.20	$144.20
7 purchase totals =	$976.22		$1,047.8596	$1,047.85	$1,047.80	$1,047.90