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	$60.97	7.389%	$65.4751	$65.48	$65.50	$65.50
Purchase #2	$14.83	3.315%	$15.3216	$15.32	$15.30	$15.30
Purchase #3	$142.84	10.161%	$157.354	$157.35	$157.35	$157.40
Purchase #4	$189.59	10.479%	$209.4571	$209.46	$209.45	$209.50
Purchase #5	$190.42	11.206%	$211.7585	$211.76	$211.75	$211.80
Purchase #6	$38.58	11.273%	$42.9291	$42.93	$42.95	$42.90
Purchase #7	$86.32	8.699%	$93.829	$93.83	$93.85	$93.80
7 purchase totals =	$723.55		$796.1244	$796.13	$796.15	$796.20