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	$59.41	10.822%	$65.8394	$65.84	$65.85	$65.80
Purchase #2	$17.33	12.330%	$19.4668	$19.47	$19.45	$19.50
Purchase #3	$86.76	11.661%	$96.8771	$96.88	$96.90	$96.90
Purchase #4	$236.46	13.734%	$268.9354	$268.94	$268.95	$268.90
Purchase #5	$9.60	4.738%	$10.0548	$10.05	$10.05	$10.10
Purchase #6	$89.43	10.151%	$98.508	$98.51	$98.50	$98.50
Purchase #7	$47.90	9.276%	$52.3432	$52.34	$52.35	$52.30
7 purchase totals =	$546.89		$612.0247	$612.03	$612.05	$612.00