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	$10.37	12.706%	$11.6876	$11.69	$11.70	$11.70
Purchase #2	$68.63	5.104%	$72.1329	$72.13	$72.15	$72.10
Purchase #3	$134.29	3.731%	$139.3004	$139.30	$139.30	$139.30
Purchase #4	$207.75	7.650%	$223.6429	$223.64	$223.65	$223.60
Purchase #5	$243.85	13.457%	$276.6649	$276.66	$276.65	$276.70
Purchase #6	$63.27	3.815%	$65.6838	$65.68	$65.70	$65.70
Purchase #7	$190.86	13.455%	$216.5402	$216.54	$216.55	$216.50
7 purchase totals =	$919.02		$1,005.6527	$1,005.64	$1,005.70	$1,005.60