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	$112.33	8.614%	$122.0061	$122.01	$122.00	$122.00
Purchase #2	$125.77	13.655%	$142.9439	$142.94	$142.95	$142.90
Purchase #3	$246.84	9.165%	$269.4629	$269.46	$269.45	$269.50
Purchase #4	$144.35	13.634%	$164.0307	$164.03	$164.05	$164.00
Purchase #5	$55.48	11.768%	$62.0089	$62.01	$62.00	$62.00
Purchase #6	$40.86	11.156%	$45.4183	$45.42	$45.40	$45.40
Purchase #7	$185.95	13.672%	$211.3731	$211.37	$211.35	$211.40
7 purchase totals =	$911.58		$1,017.2439	$1,017.24	$1,017.20	$1,017.20