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	$201.88	8.717%	$219.4779	$219.48	$219.50	$219.50
Purchase #2	$77.74	7.772%	$83.782	$83.78	$83.80	$83.80
Purchase #3	$201.54	11.690%	$225.1	$225.10	$225.10	$225.10
Purchase #4	$141.41	6.289%	$150.3033	$150.30	$150.30	$150.30
Purchase #5	$197.32	13.231%	$223.4274	$223.43	$223.45	$223.40
Purchase #6	$118.84	10.269%	$131.0437	$131.04	$131.05	$131.00
Purchase #7	$185.54	3.510%	$192.0525	$192.05	$192.05	$192.10
7 purchase totals =	$1,124.27		$1,225.1868	$1,225.18	$1,225.25	$1,225.20