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	$135.86	5.586%	$143.4491	$143.45	$143.45	$143.40
Purchase #2	$108.61	12.596%	$122.2905	$122.29	$122.30	$122.30
Purchase #3	$46.57	13.712%	$52.9557	$52.96	$52.95	$53.00
Purchase #4	$139.92	13.289%	$158.514	$158.51	$158.50	$158.50
Purchase #5	$150.66	11.342%	$167.7479	$167.75	$167.75	$167.70
Purchase #6	$115.68	6.755%	$123.4942	$123.49	$123.50	$123.50
Purchase #7	$99.92	4.200%	$104.1166	$104.12	$104.10	$104.10
7 purchase totals =	$797.22		$872.5680	$872.57	$872.55	$872.50