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	$151.38	11.254%	$168.4163	$168.42	$168.40	$168.40
Purchase #2	$61.93	11.284%	$68.9182	$68.92	$68.90	$68.90
Purchase #3	$87.95	7.851%	$94.855	$94.86	$94.85	$94.90
Purchase #4	$28.88	12.107%	$32.3765	$32.38	$32.40	$32.40
Purchase #5	$233.49	9.380%	$255.3914	$255.39	$255.40	$255.40
Purchase #6	$206.40	7.538%	$221.9584	$221.96	$221.95	$222.00
Purchase #7	$65.68	8.744%	$71.4231	$71.42	$71.40	$71.40
7 purchase totals =	$835.71		$913.3389	$913.35	$913.30	$913.40