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	$83.69	10.326%	$92.3318	$92.33	$92.35	$92.30
Purchase #2	$206.27	8.528%	$223.8607	$223.86	$223.85	$223.90
Purchase #3	$98.56	6.478%	$104.9447	$104.94	$104.95	$104.90
Purchase #4	$54.52	4.797%	$57.1353	$57.14	$57.15	$57.10
Purchase #5	$48.48	13.151%	$54.8556	$54.86	$54.85	$54.90
Purchase #6	$197.55	9.145%	$215.6159	$215.62	$215.60	$215.60
Purchase #7	$64.51	4.334%	$67.3059	$67.31	$67.30	$67.30
7 purchase totals =	$753.58		$816.0499	$816.06	$816.05	$816.00