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	$206.50	12.844%	$233.0229	$233.02	$233.00	$233.00
Purchase #2	$10.36	5.126%	$10.8911	$10.89	$10.90	$10.90
Purchase #3	$146.38	9.693%	$160.5686	$160.57	$160.55	$160.60
Purchase #4	$117.61	11.381%	$130.9952	$131.00	$131.00	$131.00
Purchase #5	$142.41	4.215%	$148.4126	$148.41	$148.40	$148.40
Purchase #6	$61.35	9.339%	$67.0795	$67.08	$67.10	$67.10
Purchase #7	$5.30	7.405%	$5.6925	$5.69	$5.70	$5.70
7 purchase totals =	$689.91		$756.6624	$756.66	$756.65	$756.70