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	$204.54	10.553%	$226.1251	$226.13	$226.15	$226.10
Purchase #2	$160.98	9.311%	$175.9688	$175.97	$175.95	$176.00
Purchase #3	$28.48	11.520%	$31.7609	$31.76	$31.75	$31.80
Purchase #4	$29.52	9.841%	$32.4251	$32.43	$32.45	$32.40
Purchase #5	$73.96	13.280%	$83.7819	$83.78	$83.80	$83.80
Purchase #6	$137.54	7.729%	$148.1705	$148.17	$148.15	$148.20
Purchase #7	$71.94	8.750%	$78.2348	$78.23	$78.25	$78.20
7 purchase totals =	$706.96		$776.4671	$776.47	$776.50	$776.50