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	$167.67	12.454%	$188.5516	$188.55	$188.55	$188.60
Purchase #2	$20.70	8.666%	$22.4939	$22.49	$22.50	$22.50
Purchase #3	$172.42	4.711%	$180.5427	$180.54	$180.55	$180.50
Purchase #4	$6.38	12.273%	$7.163	$7.16	$7.15	$7.20
Purchase #5	$62.47	4.789%	$65.4617	$65.46	$65.45	$65.50
Purchase #6	$231.86	6.297%	$246.4602	$246.46	$246.45	$246.50
Purchase #7	$78.96	9.597%	$86.5378	$86.54	$86.55	$86.50
7 purchase totals =	$740.46		$797.2109	$797.20	$797.20	$797.30