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	$63.69	6.697%	$67.9553	$67.96	$67.95	$68.00
Purchase #2	$137.34	13.658%	$156.0979	$156.10	$156.10	$156.10
Purchase #3	$235.30	3.304%	$243.0743	$243.07	$243.05	$243.10
Purchase #4	$113.26	7.656%	$121.9312	$121.93	$121.95	$121.90
Purchase #5	$78.55	6.303%	$83.501	$83.50	$83.50	$83.50
Purchase #6	$105.60	8.377%	$114.4461	$114.45	$114.45	$114.40
Purchase #7	$231.69	10.136%	$255.1741	$255.17	$255.15	$255.20
7 purchase totals =	$965.43		$1,042.1799	$1,042.18	$1,042.15	$1,042.20