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	$171.96	6.281%	$182.7608	$182.76	$182.75	$182.80
Purchase #2	$33.76	10.206%	$37.2055	$37.21	$37.20	$37.20
Purchase #3	$150.49	11.583%	$167.9213	$167.92	$167.90	$167.90
Purchase #4	$102.52	10.380%	$113.1616	$113.16	$113.15	$113.20
Purchase #5	$60.55	6.333%	$64.3846	$64.38	$64.40	$64.40
Purchase #6	$238.42	11.197%	$265.1159	$265.12	$265.10	$265.10
Purchase #7	$91.76	9.412%	$100.3965	$100.40	$100.40	$100.40
7 purchase totals =	$849.46		$930.9462	$930.95	$930.90	$931.00