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	$178.83	12.271%	$200.7742	$200.77	$200.75	$200.80
Purchase #2	$65.85	3.453%	$68.1238	$68.12	$68.10	$68.10
Purchase #3	$36.59	11.168%	$40.6764	$40.68	$40.70	$40.70
Purchase #4	$224.57	11.840%	$251.1591	$251.16	$251.15	$251.20
Purchase #5	$42.56	9.266%	$46.5036	$46.50	$46.50	$46.50
Purchase #6	$54.40	9.339%	$59.4804	$59.48	$59.50	$59.50
Purchase #7	$66.52	4.509%	$69.5194	$69.52	$69.50	$69.50
7 purchase totals =	$669.32		$736.2369	$736.23	$736.20	$736.30