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	$18.76	4.621%	$19.6269	$19.63	$19.65	$19.60
Purchase #2	$144.97	3.796%	$150.4731	$150.47	$150.45	$150.50
Purchase #3	$24.90	10.415%	$27.4933	$27.49	$27.50	$27.50
Purchase #4	$150.40	9.752%	$165.067	$165.07	$165.05	$165.10
Purchase #5	$216.89	11.750%	$242.3746	$242.37	$242.35	$242.40
Purchase #6	$249.66	4.690%	$261.3691	$261.37	$261.35	$261.40
Purchase #7	$58.88	4.514%	$61.5378	$61.54	$61.55	$61.50
7 purchase totals =	$864.46		$927.9418	$927.94	$927.90	$928.00