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	$79.83	3.328%	$82.4867	$82.49	$82.50	$82.50
Purchase #2	$244.93	5.122%	$257.4753	$257.48	$257.50	$257.50
Purchase #3	$95.65	3.166%	$98.6783	$98.68	$98.70	$98.70
Purchase #4	$56.83	5.355%	$59.8732	$59.87	$59.85	$59.90
Purchase #5	$241.41	3.476%	$249.8014	$249.80	$249.80	$249.80
Purchase #6	$117.33	11.638%	$130.9849	$130.98	$131.00	$131.00
Purchase #7	$206.56	4.614%	$216.0907	$216.09	$216.10	$216.10
7 purchase totals =	$1,042.54		$1,095.3905	$1,095.39	$1,095.45	$1,095.50