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	$35.54	6.492%	$37.8473	$37.85	$37.85	$37.80
Purchase #2	$58.43	11.297%	$65.0308	$65.03	$65.05	$65.00
Purchase #3	$229.81	11.225%	$255.6062	$255.61	$255.60	$255.60
Purchase #4	$126.76	11.777%	$141.6885	$141.69	$141.70	$141.70
Purchase #5	$54.41	4.873%	$57.0614	$57.06	$57.05	$57.10
Purchase #6	$80.59	8.789%	$87.6731	$87.67	$87.65	$87.70
Purchase #7	$248.87	6.773%	$265.726	$265.73	$265.75	$265.70
7 purchase totals =	$834.41		$910.6333	$910.64	$910.65	$910.60