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	$237.82	7.510%	$255.6803	$255.68	$255.70	$255.70
Purchase #2	$189.27	8.444%	$205.252	$205.25	$205.25	$205.30
Purchase #3	$240.90	3.646%	$249.6832	$249.68	$249.70	$249.70
Purchase #4	$55.56	6.391%	$59.1108	$59.11	$59.10	$59.10
Purchase #5	$159.61	12.491%	$179.5469	$179.55	$179.55	$179.50
Purchase #6	$116.67	12.502%	$131.2561	$131.26	$131.25	$131.30
Purchase #7	$90.38	5.602%	$95.4431	$95.44	$95.45	$95.40
7 purchase totals =	$1,090.21		$1,175.9724	$1,175.97	$1,176.00	$1,176.00