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	$39.88	7.635%	$42.9248	$42.92	$42.90	$42.90
Purchase #2	$59.86	11.538%	$66.7666	$66.77	$66.75	$66.80
Purchase #3	$217.40	9.317%	$237.6552	$237.66	$237.65	$237.70
Purchase #4	$30.92	8.148%	$33.4394	$33.44	$33.45	$33.40
Purchase #5	$220.50	5.618%	$232.8877	$232.89	$232.90	$232.90
Purchase #6	$212.45	12.458%	$238.917	$238.92	$238.90	$238.90
Purchase #7	$87.34	9.294%	$95.4574	$95.46	$95.45	$95.50
7 purchase totals =	$868.35		$948.0481	$948.06	$948.00	$948.10