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	$112.77	5.209%	$118.6442	$118.64	$118.65	$118.60
Purchase #2	$113.82	10.548%	$125.8257	$125.83	$125.85	$125.80
Purchase #3	$152.63	8.169%	$165.0983	$165.10	$165.10	$165.10
Purchase #4	$142.69	6.465%	$151.9149	$151.91	$151.90	$151.90
Purchase #5	$6.42	3.826%	$6.6656	$6.67	$6.65	$6.70
Purchase #6	$59.36	3.194%	$61.256	$61.26	$61.25	$61.30
Purchase #7	$200.32	8.294%	$216.9345	$216.93	$216.95	$216.90
7 purchase totals =	$788.01		$846.3392	$846.34	$846.35	$846.30