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	$9.94	5.310%	$10.4678	$10.47	$10.45	$10.50
Purchase #2	$46.47	4.574%	$48.5955	$48.60	$48.60	$48.60
Purchase #3	$91.93	11.537%	$102.536	$102.54	$102.55	$102.50
Purchase #4	$156.95	8.816%	$170.7867	$170.79	$170.80	$170.80
Purchase #5	$233.44	13.223%	$264.3078	$264.31	$264.30	$264.30
Purchase #6	$52.71	5.346%	$55.5279	$55.53	$55.55	$55.50
Purchase #7	$100.85	12.663%	$113.6206	$113.62	$113.60	$113.60
7 purchase totals =	$692.29		$765.8423	$765.86	$765.85	$765.80