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	$99.36	3.513%	$102.8505	$102.85	$102.85	$102.90
Purchase #2	$30.55	7.505%	$32.8428	$32.84	$32.85	$32.80
Purchase #3	$96.79	5.410%	$102.0263	$102.03	$102.05	$102.00
Purchase #4	$194.46	10.602%	$215.0766	$215.08	$215.10	$215.10
Purchase #5	$200.99	8.784%	$218.645	$218.65	$218.65	$218.60
Purchase #6	$142.43	6.835%	$152.1651	$152.17	$152.15	$152.20
Purchase #7	$142.79	8.261%	$154.5859	$154.59	$154.60	$154.60
7 purchase totals =	$907.37		$978.1922	$978.21	$978.25	$978.20