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	$71.36	10.468%	$78.83	$78.83	$78.85	$78.80
Purchase #2	$95.45	3.504%	$98.7946	$98.79	$98.80	$98.80
Purchase #3	$179.62	6.431%	$191.1714	$191.17	$191.15	$191.20
Purchase #4	$24.85	8.401%	$26.9376	$26.94	$26.95	$26.90
Purchase #5	$207.81	8.383%	$225.2307	$225.23	$225.25	$225.20
Purchase #6	$43.43	5.797%	$45.9476	$45.95	$45.95	$45.90
Purchase #7	$113.51	8.729%	$123.4183	$123.42	$123.40	$123.40
7 purchase totals =	$736.03		$790.3302	$790.33	$790.35	$790.20