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	$33.35	5.688%	$35.2469	$35.25	$35.25	$35.20
Purchase #2	$18.96	11.387%	$21.119	$21.12	$21.10	$21.10
Purchase #3	$30.38	5.514%	$32.0552	$32.06	$32.05	$32.10
Purchase #4	$145.41	13.745%	$165.3966	$165.40	$165.40	$165.40
Purchase #5	$167.71	8.621%	$182.1683	$182.17	$182.15	$182.20
Purchase #6	$94.64	9.329%	$103.469	$103.47	$103.45	$103.50
Purchase #7	$167.71	9.665%	$183.9192	$183.92	$183.90	$183.90
7 purchase totals =	$658.16		$723.3742	$723.39	$723.30	$723.40