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	$21.72	12.597%	$24.4561	$24.46	$24.45	$24.50
Purchase #2	$152.44	11.242%	$169.5773	$169.58	$169.60	$169.60
Purchase #3	$189.37	3.567%	$196.1248	$196.12	$196.10	$196.10
Purchase #4	$97.61	7.340%	$104.7746	$104.77	$104.75	$104.80
Purchase #5	$95.26	12.135%	$106.8198	$106.82	$106.80	$106.80
Purchase #6	$207.85	8.581%	$225.6856	$225.69	$225.70	$225.70
Purchase #7	$169.29	11.393%	$188.5772	$188.58	$188.60	$188.60
7 purchase totals =	$933.54		$1,016.0154	$1,016.02	$1,016.00	$1,016.10