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	$174.49	10.437%	$192.7015	$192.70	$192.70	$192.70
Purchase #2	$28.40	4.469%	$29.6692	$29.67	$29.65	$29.70
Purchase #3	$241.86	9.102%	$263.8741	$263.87	$263.85	$263.90
Purchase #4	$184.65	10.696%	$204.4002	$204.40	$204.40	$204.40
Purchase #5	$85.83	5.808%	$90.815	$90.82	$90.80	$90.80
Purchase #6	$27.29	4.473%	$28.5107	$28.51	$28.50	$28.50
Purchase #7	$152.93	10.185%	$168.5059	$168.51	$168.50	$168.50
7 purchase totals =	$895.45		$978.4766	$978.48	$978.40	$978.50