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	$56.39	5.850%	$59.6888	$59.69	$59.70	$59.70
Purchase #2	$118.67	5.632%	$125.3535	$125.35	$125.35	$125.40
Purchase #3	$104.58	3.798%	$108.5519	$108.55	$108.55	$108.60
Purchase #4	$61.47	6.328%	$65.3598	$65.36	$65.35	$65.40
Purchase #5	$62.60	12.862%	$70.6516	$70.65	$70.65	$70.70
Purchase #6	$155.81	7.499%	$167.4942	$167.49	$167.50	$167.50
Purchase #7	$179.77	3.401%	$185.884	$185.88	$185.90	$185.90
7 purchase totals =	$739.29		$782.9838	$782.97	$783.00	$783.20