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	$6.90	13.541%	$7.8343	$7.83	$7.85	$7.80
Purchase #2	$67.41	7.576%	$72.517	$72.52	$72.50	$72.50
Purchase #3	$154.46	13.712%	$175.6396	$175.64	$175.65	$175.60
Purchase #4	$84.54	5.146%	$88.8904	$88.89	$88.90	$88.90
Purchase #5	$94.30	6.638%	$100.5596	$100.56	$100.55	$100.60
Purchase #6	$236.87	12.628%	$266.7819	$266.78	$266.80	$266.80
Purchase #7	$90.36	7.721%	$97.3367	$97.34	$97.35	$97.30
7 purchase totals =	$734.84		$809.5595	$809.56	$809.60	$809.50