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	$154.41	9.365%	$168.8705	$168.87	$168.85	$168.90
Purchase #2	$132.74	10.806%	$147.0839	$147.08	$147.10	$147.10
Purchase #3	$31.31	8.542%	$33.9845	$33.98	$34.00	$34.00
Purchase #4	$122.41	7.818%	$131.98	$131.98	$132.00	$132.00
Purchase #5	$34.95	6.457%	$37.2067	$37.21	$37.20	$37.20
Purchase #6	$94.51	9.326%	$103.324	$103.32	$103.30	$103.30
Purchase #7	$79.39	4.754%	$83.1642	$83.16	$83.15	$83.20
7 purchase totals =	$649.72		$705.6138	$705.60	$705.60	$705.70