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	$115.90	9.496%	$126.9059	$126.91	$126.90	$126.90
Purchase #2	$55.34	13.603%	$62.8679	$62.87	$62.85	$62.90
Purchase #3	$174.83	12.153%	$196.0771	$196.08	$196.10	$196.10
Purchase #4	$243.93	4.285%	$254.3824	$254.38	$254.40	$254.40
Purchase #5	$49.26	10.345%	$54.3559	$54.36	$54.35	$54.40
Purchase #6	$195.91	13.579%	$222.5126	$222.51	$222.50	$222.50
Purchase #7	$84.32	8.262%	$91.2865	$91.29	$91.30	$91.30
7 purchase totals =	$919.49		$1,008.3883	$1,008.40	$1,008.40	$1,008.50