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	$190.62	13.345%	$216.0582	$216.06	$216.05	$216.10
Purchase #2	$217.80	4.500%	$227.601	$227.60	$227.60	$227.60
Purchase #3	$77.44	6.320%	$82.3342	$82.33	$82.35	$82.30
Purchase #4	$36.74	12.476%	$41.3237	$41.32	$41.30	$41.30
Purchase #5	$139.61	7.593%	$150.2106	$150.21	$150.20	$150.20
Purchase #6	$163.27	9.740%	$179.1725	$179.17	$179.15	$179.20
Purchase #7	$178.54	6.747%	$190.5861	$190.59	$190.60	$190.60
7 purchase totals =	$1,004.02		$1,087.2863	$1,087.28	$1,087.25	$1,087.30