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	$34.83	7.371%	$37.3973	$37.40	$37.40	$37.40
Purchase #2	$131.37	8.391%	$142.3933	$142.39	$142.40	$142.40
Purchase #3	$236.41	12.147%	$265.1267	$265.13	$265.15	$265.10
Purchase #4	$149.27	12.697%	$168.2228	$168.22	$168.20	$168.20
Purchase #5	$155.59	4.177%	$162.089	$162.09	$162.10	$162.10
Purchase #6	$49.71	11.809%	$55.5803	$55.58	$55.60	$55.60
Purchase #7	$44.48	12.531%	$50.0538	$50.05	$50.05	$50.10
7 purchase totals =	$801.66		$880.8632	$880.86	$880.90	$880.90