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	$119.36	12.595%	$134.3934	$134.39	$134.40	$134.40
Purchase #2	$109.38	8.150%	$118.2945	$118.29	$118.30	$118.30
Purchase #3	$236.27	8.553%	$256.4782	$256.48	$256.50	$256.50
Purchase #4	$47.82	8.391%	$51.8326	$51.83	$51.85	$51.80
Purchase #5	$127.83	5.435%	$134.7776	$134.78	$134.80	$134.80
Purchase #6	$227.64	7.761%	$245.3071	$245.31	$245.30	$245.30
Purchase #7	$167.73	13.418%	$190.236	$190.24	$190.25	$190.20
7 purchase totals =	$1,036.03		$1,131.3194	$1,131.32	$1,131.40	$1,131.30