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	$208.99	7.595%	$224.8628	$224.86	$224.85	$224.90
Purchase #2	$44.83	7.248%	$48.0793	$48.08	$48.10	$48.10
Purchase #3	$41.82	8.353%	$45.3132	$45.31	$45.30	$45.30
Purchase #4	$68.64	11.168%	$76.3057	$76.31	$76.30	$76.30
Purchase #5	$42.35	8.435%	$45.9222	$45.92	$45.90	$45.90
Purchase #6	$200.28	5.815%	$211.9263	$211.93	$211.95	$211.90
Purchase #7	$7.40	5.856%	$7.8333	$7.83	$7.85	$7.80
7 purchase totals =	$614.31		$660.2428	$660.24	$660.25	$660.20