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	$241.64	11.570%	$269.5977	$269.60	$269.60	$269.60
Purchase #2	$82.47	10.374%	$91.0254	$91.03	$91.05	$91.00
Purchase #3	$113.57	12.567%	$127.8423	$127.84	$127.85	$127.80
Purchase #4	$192.80	12.283%	$216.4816	$216.48	$216.50	$216.50
Purchase #5	$121.77	7.620%	$131.0489	$131.05	$131.05	$131.00
Purchase #6	$165.78	12.483%	$186.4743	$186.47	$186.45	$186.50
Purchase #7	$197.91	12.472%	$222.5933	$222.59	$222.60	$222.60
7 purchase totals =	$1,115.94		$1,245.0635	$1,245.06	$1,245.10	$1,245.00