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	$204.49	9.479%	$223.8736	$223.87	$223.85	$223.90
Purchase #2	$176.86	5.779%	$187.0807	$187.08	$187.10	$187.10
Purchase #3	$33.93	4.491%	$35.4538	$35.45	$35.45	$35.50
Purchase #4	$12.55	4.134%	$13.0688	$13.07	$13.05	$13.10
Purchase #5	$150.74	5.123%	$158.4624	$158.46	$158.45	$158.50
Purchase #6	$65.91	11.473%	$73.4719	$73.47	$73.45	$73.50
Purchase #7	$229.61	5.158%	$241.4533	$241.45	$241.45	$241.50
7 purchase totals =	$874.09		$932.8645	$932.85	$932.80	$933.10