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	$205.46	9.500%	$224.9787	$224.98	$225.00	$225.00
Purchase #2	$121.38	6.139%	$128.8315	$128.83	$128.85	$128.80
Purchase #3	$125.32	4.753%	$131.2765	$131.28	$131.30	$131.30
Purchase #4	$29.52	6.257%	$31.3671	$31.37	$31.35	$31.40
Purchase #5	$30.93	11.239%	$34.4062	$34.41	$34.40	$34.40
Purchase #6	$41.50	11.478%	$46.2634	$46.26	$46.25	$46.30
Purchase #7	$65.77	6.414%	$69.9885	$69.99	$70.00	$70.00
7 purchase totals =	$619.88		$667.1119	$667.12	$667.15	$667.20