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	$24.81	5.191%	$26.0979	$26.10	$26.10	$26.10
Purchase #2	$36.71	10.190%	$40.4507	$40.45	$40.45	$40.50
Purchase #3	$104.88	7.862%	$113.1257	$113.13	$113.15	$113.10
Purchase #4	$36.38	12.448%	$40.9086	$40.91	$40.90	$40.90
Purchase #5	$170.77	13.649%	$194.0784	$194.08	$194.10	$194.10
Purchase #6	$55.57	6.248%	$59.042	$59.04	$59.05	$59.00
Purchase #7	$174.77	9.781%	$191.8643	$191.86	$191.85	$191.90
7 purchase totals =	$603.89		$665.5676	$665.57	$665.60	$665.60