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	$164.54	4.431%	$171.8308	$171.83	$171.85	$171.80
Purchase #2	$215.72	10.415%	$238.1872	$238.19	$238.20	$238.20
Purchase #3	$131.43	11.115%	$146.0384	$146.04	$146.05	$146.00
Purchase #4	$151.96	10.744%	$168.2866	$168.29	$168.30	$168.30
Purchase #5	$51.50	4.679%	$53.9097	$53.91	$53.90	$53.90
Purchase #6	$236.95	10.549%	$261.9459	$261.95	$261.95	$261.90
Purchase #7	$52.39	4.332%	$54.6595	$54.66	$54.65	$54.70
7 purchase totals =	$1,004.49		$1,094.8581	$1,094.87	$1,094.90	$1,094.80