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	$67.72	7.802%	$73.0035	$73.00	$73.00	$73.00
Purchase #2	$95.71	7.549%	$102.9351	$102.94	$102.95	$102.90
Purchase #3	$20.58	5.801%	$21.7738	$21.77	$21.75	$21.80
Purchase #4	$151.67	4.465%	$158.4421	$158.44	$158.45	$158.40
Purchase #5	$70.86	10.769%	$78.4909	$78.49	$78.50	$78.50
Purchase #6	$201.29	4.216%	$209.7764	$209.78	$209.80	$209.80
Purchase #7	$49.49	12.835%	$55.842	$55.84	$55.85	$55.80
7 purchase totals =	$657.32		$700.2638	$700.26	$700.30	$700.20