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	$108.32	7.508%	$116.4527	$116.45	$116.45	$116.50
Purchase #2	$171.53	8.651%	$186.3691	$186.37	$186.35	$186.40
Purchase #3	$16.41	13.762%	$18.6683	$18.67	$18.65	$18.70
Purchase #4	$246.93	3.283%	$255.0367	$255.04	$255.05	$255.00
Purchase #5	$171.95	11.245%	$191.2858	$191.29	$191.30	$191.30
Purchase #6	$66.81	6.452%	$71.1206	$71.12	$71.10	$71.10
Purchase #7	$229.64	12.642%	$258.6711	$258.67	$258.65	$258.70
7 purchase totals =	$1,011.59		$1,097.6043	$1,097.61	$1,097.55	$1,097.70