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	$134.73	5.623%	$142.3059	$142.31	$142.30	$142.30
Purchase #2	$125.92	6.225%	$133.7585	$133.76	$133.75	$133.80
Purchase #3	$197.70	7.461%	$212.4504	$212.45	$212.45	$212.50
Purchase #4	$100.83	4.638%	$105.5065	$105.51	$105.50	$105.50
Purchase #5	$113.65	5.309%	$119.6837	$119.68	$119.70	$119.70
Purchase #6	$205.75	11.664%	$229.7487	$229.75	$229.75	$229.70
Purchase #7	$161.31	4.400%	$168.4076	$168.41	$168.40	$168.40
7 purchase totals =	$1,039.89		$1,111.8613	$1,111.87	$1,111.85	$1,111.90