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	$217.60	9.604%	$238.4983	$238.50	$238.50	$238.50
Purchase #2	$167.92	6.404%	$178.6736	$178.67	$178.65	$178.70
Purchase #3	$212.26	12.478%	$238.7458	$238.75	$238.75	$238.70
Purchase #4	$131.50	12.655%	$148.1413	$148.14	$148.15	$148.10
Purchase #5	$93.54	5.696%	$98.868	$98.87	$98.85	$98.90
Purchase #6	$49.98	10.625%	$55.2904	$55.29	$55.30	$55.30
Purchase #7	$107.51	5.810%	$113.7563	$113.76	$113.75	$113.80
7 purchase totals =	$980.31		$1,071.9737	$1,071.98	$1,071.95	$1,072.00