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	$88.69	9.863%	$97.4375	$97.44	$97.45	$97.40
Purchase #2	$71.33	5.556%	$75.2931	$75.29	$75.30	$75.30
Purchase #3	$33.51	11.442%	$37.3442	$37.34	$37.35	$37.30
Purchase #4	$91.38	12.287%	$102.6079	$102.61	$102.60	$102.60
Purchase #5	$215.37	12.818%	$242.9761	$242.98	$243.00	$243.00
Purchase #6	$242.98	5.217%	$255.6563	$255.66	$255.65	$255.70
Purchase #7	$113.35	12.480%	$127.4961	$127.50	$127.50	$127.50
7 purchase totals =	$856.61		$938.8112	$938.82	$938.85	$938.80