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	$160.73	7.313%	$172.4842	$172.48	$172.50	$172.50
Purchase #2	$188.59	6.454%	$200.7616	$200.76	$200.75	$200.80
Purchase #3	$185.76	12.682%	$209.3181	$209.32	$209.30	$209.30
Purchase #4	$25.60	7.761%	$27.5868	$27.59	$27.60	$27.60
Purchase #5	$78.37	10.465%	$86.5714	$86.57	$86.55	$86.60
Purchase #6	$210.45	6.748%	$224.6512	$224.65	$224.65	$224.70
Purchase #7	$121.77	6.194%	$129.3124	$129.31	$129.30	$129.30
7 purchase totals =	$971.27		$1,050.6857	$1,050.68	$1,050.65	$1,050.80