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	$201.40	10.868%	$223.2882	$223.29	$223.30	$223.30
Purchase #2	$86.74	5.835%	$91.8013	$91.80	$91.80	$91.80
Purchase #3	$12.43	8.303%	$13.4621	$13.46	$13.45	$13.50
Purchase #4	$150.34	5.397%	$158.4538	$158.45	$158.45	$158.50
Purchase #5	$45.53	10.116%	$50.1358	$50.14	$50.15	$50.10
Purchase #6	$88.43	7.186%	$94.7846	$94.78	$94.80	$94.80
Purchase #7	$104.78	4.582%	$109.581	$109.58	$109.60	$109.60
7 purchase totals =	$689.65		$741.5068	$741.50	$741.55	$741.60