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	$146.60	13.143%	$165.8676	$165.87	$165.85	$165.90
Purchase #2	$153.81	6.824%	$164.306	$164.31	$164.30	$164.30
Purchase #3	$209.29	3.248%	$216.0877	$216.09	$216.10	$216.10
Purchase #4	$162.93	10.246%	$179.6238	$179.62	$179.60	$179.60
Purchase #5	$47.53	6.431%	$50.5867	$50.59	$50.60	$50.60
Purchase #6	$84.87	13.191%	$96.0652	$96.07	$96.05	$96.10
Purchase #7	$143.75	7.143%	$154.0181	$154.02	$154.00	$154.00
7 purchase totals =	$948.78		$1,026.5551	$1,026.57	$1,026.50	$1,026.60