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	$61.90	8.633%	$67.2438	$67.24	$67.25	$67.20
Purchase #2	$250.27	6.795%	$267.2758	$267.28	$267.30	$267.30
Purchase #3	$37.47	3.174%	$38.6593	$38.66	$38.65	$38.70
Purchase #4	$13.57	7.211%	$14.5485	$14.55	$14.55	$14.50
Purchase #5	$223.94	6.497%	$238.4894	$238.49	$238.50	$238.50
Purchase #6	$127.70	13.360%	$144.7607	$144.76	$144.75	$144.80
Purchase #7	$57.32	10.477%	$63.3254	$63.33	$63.35	$63.30
7 purchase totals =	$772.17		$834.3029	$834.31	$834.35	$834.30