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	$139.95	5.757%	$148.0069	$148.01	$148.00	$148.00
Purchase #2	$137.59	5.605%	$145.3019	$145.30	$145.30	$145.30
Purchase #3	$59.77	3.275%	$61.7275	$61.73	$61.75	$61.70
Purchase #4	$10.47	9.780%	$11.494	$11.49	$11.50	$11.50
Purchase #5	$187.64	11.304%	$208.8508	$208.85	$208.85	$208.90
Purchase #6	$231.48	4.500%	$241.8966	$241.90	$241.90	$241.90
Purchase #7	$91.40	10.562%	$101.0537	$101.05	$101.05	$101.10
7 purchase totals =	$858.30		$918.3314	$918.33	$918.35	$918.40