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	$80.56	12.780%	$90.8556	$90.86	$90.85	$90.90
Purchase #2	$217.49	10.276%	$239.8393	$239.84	$239.85	$239.80
Purchase #3	$187.27	4.822%	$196.3002	$196.30	$196.30	$196.30
Purchase #4	$97.72	3.130%	$100.7786	$100.78	$100.80	$100.80
Purchase #5	$222.53	8.306%	$241.0133	$241.01	$241.00	$241.00
Purchase #6	$112.87	5.387%	$118.9503	$118.95	$118.95	$119.00
Purchase #7	$99.27	8.415%	$107.6236	$107.62	$107.60	$107.60
7 purchase totals =	$1,017.71		$1,095.3609	$1,095.36	$1,095.35	$1,095.40