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	$162.44	10.290%	$179.1551	$179.16	$179.15	$179.20
Purchase #2	$57.28	4.638%	$59.9366	$59.94	$59.95	$59.90
Purchase #3	$155.61	3.789%	$161.5061	$161.51	$161.50	$161.50
Purchase #4	$32.65	7.657%	$35.15	$35.15	$35.15	$35.20
Purchase #5	$233.64	5.521%	$246.5393	$246.54	$246.55	$246.50
Purchase #6	$154.95	3.440%	$160.2803	$160.28	$160.30	$160.30
Purchase #7	$83.81	9.679%	$91.922	$91.92	$91.90	$91.90
7 purchase totals =	$880.38		$934.4894	$934.50	$934.50	$934.50