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	$88.83	6.706%	$94.7869	$94.79	$94.80	$94.80
Purchase #2	$31.73	3.625%	$32.8802	$32.88	$32.90	$32.90
Purchase #3	$81.71	4.650%	$85.5095	$85.51	$85.50	$85.50
Purchase #4	$94.75	11.710%	$105.8452	$105.85	$105.85	$105.80
Purchase #5	$72.28	5.473%	$76.2359	$76.24	$76.25	$76.20
Purchase #6	$144.92	5.487%	$152.8718	$152.87	$152.85	$152.90
Purchase #7	$96.58	9.196%	$105.4615	$105.46	$105.45	$105.50
7 purchase totals =	$610.80		$653.5910	$653.60	$653.60	$653.60