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	$66.29	8.176%	$71.7099	$71.71	$71.70	$71.70
Purchase #2	$200.61	3.433%	$207.4969	$207.50	$207.50	$207.50
Purchase #3	$200.46	7.778%	$216.0518	$216.05	$216.05	$216.10
Purchase #4	$106.50	4.695%	$111.5002	$111.50	$111.50	$111.50
Purchase #5	$52.86	12.188%	$59.3026	$59.30	$59.30	$59.30
Purchase #6	$191.94	6.513%	$204.4411	$204.44	$204.45	$204.40
Purchase #7	$208.27	6.535%	$221.8804	$221.88	$221.90	$221.90
7 purchase totals =	$1,026.93		$1,092.3829	$1,092.38	$1,092.40	$1,092.40