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	$65.66	10.587%	$72.6114	$72.61	$72.60	$72.60
Purchase #2	$34.43	4.802%	$36.0833	$36.08	$36.10	$36.10
Purchase #3	$155.69	5.623%	$164.4444	$164.44	$164.45	$164.40
Purchase #4	$90.76	4.740%	$95.062	$95.06	$95.05	$95.10
Purchase #5	$237.55	3.102%	$244.9188	$244.92	$244.90	$244.90
Purchase #6	$207.34	6.241%	$220.2801	$220.28	$220.30	$220.30
Purchase #7	$35.89	6.129%	$38.0897	$38.09	$38.10	$38.10
7 purchase totals =	$827.32		$871.4897	$871.48	$871.50	$871.50