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	$205.36	13.836%	$233.7736	$233.77	$233.75	$233.80
Purchase #2	$160.49	4.778%	$168.1582	$168.16	$168.15	$168.20
Purchase #3	$89.36	5.462%	$94.2408	$94.24	$94.25	$94.20
Purchase #4	$30.32	8.391%	$32.8642	$32.86	$32.85	$32.90
Purchase #5	$146.86	10.361%	$162.0762	$162.08	$162.10	$162.10
Purchase #6	$167.69	4.402%	$175.0717	$175.07	$175.05	$175.10
Purchase #7	$54.52	9.384%	$59.6362	$59.64	$59.65	$59.60
7 purchase totals =	$854.60		$925.8209	$925.82	$925.80	$925.90