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	$236.95	5.414%	$249.7785	$249.78	$249.80	$249.80
Purchase #2	$217.32	10.238%	$239.5692	$239.57	$239.55	$239.60
Purchase #3	$241.58	11.842%	$270.1879	$270.19	$270.20	$270.20
Purchase #4	$34.43	9.139%	$37.5766	$37.58	$37.60	$37.60
Purchase #5	$159.71	7.558%	$171.7809	$171.78	$171.80	$171.80
Purchase #6	$167.88	7.858%	$181.072	$181.07	$181.05	$181.10
Purchase #7	$141.86	6.367%	$150.8922	$150.89	$150.90	$150.90
7 purchase totals =	$1,199.73		$1,300.8573	$1,300.86	$1,300.90	$1,301.00