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	$76.96	10.442%	$84.9962	$85.00	$85.00	$85.00
Purchase #2	$102.60	12.650%	$115.5789	$115.58	$115.60	$115.60
Purchase #3	$215.49	3.394%	$222.8037	$222.80	$222.80	$222.80
Purchase #4	$95.49	4.448%	$99.7374	$99.74	$99.75	$99.70
Purchase #5	$69.44	13.345%	$78.7068	$78.71	$78.70	$78.70
Purchase #6	$85.64	6.490%	$91.198	$91.20	$91.20	$91.20
Purchase #7	$143.56	10.669%	$158.8764	$158.88	$158.90	$158.90
7 purchase totals =	$789.18		$851.8974	$851.91	$851.95	$851.90