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	$51.30	12.775%	$57.8536	$57.85	$57.85	$57.90
Purchase #2	$10.29	5.209%	$10.826	$10.83	$10.85	$10.80
Purchase #3	$132.81	13.185%	$150.321	$150.32	$150.30	$150.30
Purchase #4	$132.78	6.772%	$141.7719	$141.77	$141.75	$141.80
Purchase #5	$12.84	5.377%	$13.5304	$13.53	$13.55	$13.50
Purchase #6	$98.69	11.382%	$109.9229	$109.92	$109.90	$109.90
Purchase #7	$130.48	13.304%	$147.8391	$147.84	$147.85	$147.80
7 purchase totals =	$569.19		$632.0649	$632.06	$632.05	$632.00