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	$72.93	13.194%	$82.5524	$82.55	$82.55	$82.60
Purchase #2	$85.74	5.827%	$90.7361	$90.74	$90.75	$90.70
Purchase #3	$135.45	5.451%	$142.8334	$142.83	$142.85	$142.80
Purchase #4	$52.76	11.263%	$58.7024	$58.70	$58.70	$58.70
Purchase #5	$105.34	5.486%	$111.119	$111.12	$111.10	$111.10
Purchase #6	$149.90	13.811%	$170.6027	$170.60	$170.60	$170.60
Purchase #7	$94.83	9.502%	$103.8407	$103.84	$103.85	$103.80
7 purchase totals =	$696.95		$760.3867	$760.38	$760.40	$760.30