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	$221.43	3.423%	$229.0095	$229.01	$229.00	$229.00
Purchase #2	$86.53	6.652%	$92.286	$92.29	$92.30	$92.30
Purchase #3	$218.60	3.603%	$226.4762	$226.48	$226.50	$226.50
Purchase #4	$26.64	6.483%	$28.3671	$28.37	$28.35	$28.40
Purchase #5	$200.48	3.683%	$207.8637	$207.86	$207.85	$207.90
Purchase #6	$113.72	12.215%	$127.6109	$127.61	$127.60	$127.60
Purchase #7	$132.28	5.401%	$139.4244	$139.42	$139.40	$139.40
7 purchase totals =	$999.68		$1,051.0378	$1,051.04	$1,051.00	$1,051.10