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	$150.53	8.191%	$162.8599	$162.86	$162.85	$162.90
Purchase #2	$184.27	6.592%	$196.4171	$196.42	$196.40	$196.40
Purchase #3	$133.37	7.846%	$143.8342	$143.83	$143.85	$143.80
Purchase #4	$149.55	4.712%	$156.5968	$156.60	$156.60	$156.60
Purchase #5	$64.63	10.776%	$71.5945	$71.59	$71.60	$71.60
Purchase #6	$95.42	5.749%	$100.9057	$100.91	$100.90	$100.90
Purchase #7	$191.65	3.872%	$199.0707	$199.07	$199.05	$199.10
7 purchase totals =	$969.42		$1,031.2789	$1,031.28	$1,031.25	$1,031.30