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	$82.43	4.741%	$86.338	$86.34	$86.35	$86.30
Purchase #2	$193.51	13.656%	$219.9357	$219.94	$219.95	$219.90
Purchase #3	$151.43	9.281%	$165.4842	$165.48	$165.50	$165.50
Purchase #4	$73.76	10.589%	$81.5704	$81.57	$81.55	$81.60
Purchase #5	$219.85	13.158%	$248.7779	$248.78	$248.80	$248.80
Purchase #6	$144.37	8.394%	$156.4884	$156.49	$156.50	$156.50
Purchase #7	$52.41	3.686%	$54.3418	$54.34	$54.35	$54.30
7 purchase totals =	$917.76		$1,012.9364	$1,012.94	$1,013.00	$1,012.90