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	$186.81	10.544%	$206.5072	$206.51	$206.50	$206.50
Purchase #2	$75.78	5.473%	$79.9274	$79.93	$79.95	$79.90
Purchase #3	$28.98	10.497%	$32.022	$32.02	$32.00	$32.00
Purchase #4	$140.97	3.798%	$146.324	$146.32	$146.30	$146.30
Purchase #5	$82.50	8.235%	$89.2939	$89.29	$89.30	$89.30
Purchase #6	$37.28	9.670%	$40.885	$40.89	$40.90	$40.90
Purchase #7	$180.73	3.866%	$187.717	$187.72	$187.70	$187.70
7 purchase totals =	$733.05		$782.6765	$782.68	$782.65	$782.60