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	$77.33	6.789%	$82.5799	$82.58	$82.60	$82.60
Purchase #2	$218.36	13.853%	$248.6094	$248.61	$248.60	$248.60
Purchase #3	$232.55	11.176%	$258.5398	$258.54	$258.55	$258.50
Purchase #4	$28.92	13.561%	$32.8418	$32.84	$32.85	$32.80
Purchase #5	$151.30	3.148%	$156.0629	$156.06	$156.05	$156.10
Purchase #6	$174.29	13.555%	$197.915	$197.92	$197.90	$197.90
Purchase #7	$32.39	6.407%	$34.4652	$34.47	$34.45	$34.50
7 purchase totals =	$915.14		$1,011.0140	$1,011.02	$1,011.00	$1,011.00