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	$130.86	7.473%	$140.6392	$140.64	$140.65	$140.60
Purchase #2	$146.75	5.180%	$154.3517	$154.35	$154.35	$154.40
Purchase #3	$35.51	9.406%	$38.8501	$38.85	$38.85	$38.90
Purchase #4	$117.83	8.557%	$127.9127	$127.91	$127.90	$127.90
Purchase #5	$172.81	6.735%	$184.4488	$184.45	$184.45	$184.40
Purchase #6	$208.76	3.400%	$215.8578	$215.86	$215.85	$215.90
Purchase #7	$114.28	6.435%	$121.6339	$121.63	$121.65	$121.60
7 purchase totals =	$926.80		$983.6942	$983.69	$983.70	$983.70