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	$94.66	5.725%	$100.0793	$100.08	$100.10	$100.10
Purchase #2	$32.58	7.490%	$35.0202	$35.02	$35.00	$35.00
Purchase #3	$219.77	12.406%	$247.0347	$247.03	$247.05	$247.00
Purchase #4	$187.32	4.640%	$196.0116	$196.01	$196.00	$196.00
Purchase #5	$39.63	5.714%	$41.8945	$41.89	$41.90	$41.90
Purchase #6	$154.27	12.376%	$173.3625	$173.36	$173.35	$173.40
Purchase #7	$93.47	12.440%	$105.0977	$105.10	$105.10	$105.10
7 purchase totals =	$821.70		$898.5005	$898.49	$898.50	$898.50