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	$219.59	4.666%	$229.8361	$229.84	$229.85	$229.80
Purchase #2	$89.26	6.871%	$95.3931	$95.39	$95.40	$95.40
Purchase #3	$24.48	11.217%	$27.2259	$27.23	$27.25	$27.20
Purchase #4	$30.96	11.109%	$34.3993	$34.40	$34.40	$34.40
Purchase #5	$146.31	4.266%	$152.5516	$152.55	$152.55	$152.60
Purchase #6	$247.84	13.355%	$280.939	$280.94	$280.95	$280.90
Purchase #7	$60.25	9.853%	$66.1864	$66.19	$66.20	$66.20
7 purchase totals =	$818.69		$886.5314	$886.54	$886.60	$886.50