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	$82.50	10.250%	$90.9563	$90.96	$90.95	$91.00
Purchase #2	$222.74	10.576%	$246.297	$246.30	$246.30	$246.30
Purchase #3	$145.55	12.267%	$163.4046	$163.40	$163.40	$163.40
Purchase #4	$42.57	13.435%	$48.2893	$48.29	$48.30	$48.30
Purchase #5	$160.84	13.225%	$182.1111	$182.11	$182.10	$182.10
Purchase #6	$228.68	5.294%	$240.7863	$240.79	$240.80	$240.80
Purchase #7	$100.57	4.417%	$105.0122	$105.01	$105.00	$105.00
7 purchase totals =	$983.45		$1,076.8568	$1,076.86	$1,076.85	$1,076.90