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	$152.93	8.483%	$165.9031	$165.90	$165.90	$165.90
Purchase #2	$113.63	13.161%	$128.5848	$128.58	$128.60	$128.60
Purchase #3	$87.34	6.741%	$93.2276	$93.23	$93.25	$93.20
Purchase #4	$213.70	4.286%	$222.8592	$222.86	$222.85	$222.90
Purchase #5	$159.64	4.138%	$166.2459	$166.25	$166.25	$166.20
Purchase #6	$164.53	12.647%	$185.3381	$185.34	$185.35	$185.30
Purchase #7	$186.37	5.469%	$196.5626	$196.56	$196.55	$196.60
7 purchase totals =	$1,078.14		$1,158.7213	$1,158.72	$1,158.75	$1,158.70