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	$246.46	8.665%	$267.8158	$267.82	$267.80	$267.80
Purchase #2	$240.33	12.548%	$270.4866	$270.49	$270.50	$270.50
Purchase #3	$56.62	4.634%	$59.2438	$59.24	$59.25	$59.20
Purchase #4	$235.85	8.171%	$255.1213	$255.12	$255.10	$255.10
Purchase #5	$198.75	8.293%	$215.2323	$215.23	$215.25	$215.20
Purchase #6	$199.87	11.792%	$223.4387	$223.44	$223.45	$223.40
Purchase #7	$220.74	3.330%	$228.0906	$228.09	$228.10	$228.10
7 purchase totals =	$1,398.62		$1,519.4291	$1,519.43	$1,519.45	$1,519.30