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	$76.32	13.274%	$86.4507	$86.45	$86.45	$86.50
Purchase #2	$191.88	5.700%	$202.8172	$202.82	$202.80	$202.80
Purchase #3	$139.59	11.813%	$156.0798	$156.08	$156.10	$156.10
Purchase #4	$105.91	12.488%	$119.136	$119.14	$119.15	$119.10
Purchase #5	$209.53	5.657%	$221.3831	$221.38	$221.40	$221.40
Purchase #6	$139.50	3.218%	$143.9891	$143.99	$144.00	$144.00
Purchase #7	$131.31	8.837%	$142.9139	$142.91	$142.90	$142.90
7 purchase totals =	$994.04		$1,072.7698	$1,072.77	$1,072.80	$1,072.80