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	$88.97	6.348%	$94.6178	$94.62	$94.60	$94.60
Purchase #2	$108.45	13.248%	$122.8175	$122.82	$122.80	$122.80
Purchase #3	$118.37	10.435%	$130.7219	$130.72	$130.70	$130.70
Purchase #4	$93.46	6.535%	$99.5676	$99.57	$99.55	$99.60
Purchase #5	$78.92	13.171%	$89.3146	$89.31	$89.30	$89.30
Purchase #6	$234.94	6.238%	$249.5956	$249.60	$249.60	$249.60
Purchase #7	$41.40	11.171%	$46.0248	$46.02	$46.00	$46.00
7 purchase totals =	$764.51		$832.6598	$832.66	$832.55	$832.60