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	$123.39	6.456%	$131.3561	$131.36	$131.35	$131.40
Purchase #2	$95.48	5.351%	$100.5891	$100.59	$100.60	$100.60
Purchase #3	$105.31	4.177%	$109.7088	$109.71	$109.70	$109.70
Purchase #4	$159.97	12.174%	$179.4447	$179.44	$179.45	$179.40
Purchase #5	$87.51	5.240%	$92.0955	$92.10	$92.10	$92.10
Purchase #6	$157.98	6.415%	$168.1144	$168.11	$168.10	$168.10
Purchase #7	$97.84	8.485%	$106.1417	$106.14	$106.15	$106.10
7 purchase totals =	$827.48		$887.4503	$887.45	$887.45	$887.40