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	$77.94	12.483%	$87.6693	$87.67	$87.65	$87.70
Purchase #2	$113.83	13.790%	$129.5272	$129.53	$129.55	$129.50
Purchase #3	$239.32	7.185%	$256.5151	$256.52	$256.50	$256.50
Purchase #4	$101.56	7.686%	$109.3659	$109.37	$109.35	$109.40
Purchase #5	$84.45	10.131%	$93.0056	$93.01	$93.00	$93.00
Purchase #6	$231.86	13.535%	$263.2423	$263.24	$263.25	$263.20
Purchase #7	$108.93	11.746%	$121.7249	$121.72	$121.70	$121.70
7 purchase totals =	$957.89		$1,061.0503	$1,061.06	$1,061.00	$1,061.00