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	$106.94	5.237%	$112.5404	$112.54	$112.55	$112.50
Purchase #2	$36.96	13.533%	$41.9618	$41.96	$41.95	$42.00
Purchase #3	$54.43	11.361%	$60.6138	$60.61	$60.60	$60.60
Purchase #4	$105.52	11.868%	$118.0431	$118.04	$118.05	$118.00
Purchase #5	$91.83	6.237%	$97.5574	$97.56	$97.55	$97.60
Purchase #6	$108.87	3.129%	$112.2765	$112.28	$112.30	$112.30
Purchase #7	$12.89	3.517%	$13.3433	$13.34	$13.35	$13.30
7 purchase totals =	$517.44		$556.3363	$556.33	$556.35	$556.30