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	$144.83	11.549%	$161.5564	$161.56	$161.55	$161.60
Purchase #2	$152.87	10.163%	$168.4062	$168.41	$168.40	$168.40
Purchase #3	$113.85	13.840%	$129.6068	$129.61	$129.60	$129.60
Purchase #4	$50.27	13.431%	$57.0218	$57.02	$57.00	$57.00
Purchase #5	$73.42	11.753%	$82.0491	$82.05	$82.05	$82.00
Purchase #6	$216.78	4.669%	$226.9015	$226.90	$226.90	$226.90
Purchase #7	$160.27	7.191%	$171.795	$171.80	$171.80	$171.80
7 purchase totals =	$912.29		$997.3368	$997.35	$997.30	$997.30