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	$86.77	9.400%	$94.9264	$94.93	$94.95	$94.90
Purchase #2	$142.48	6.590%	$151.8694	$151.87	$151.85	$151.90
Purchase #3	$183.71	13.851%	$209.1557	$209.16	$209.15	$209.20
Purchase #4	$156.68	5.767%	$165.7157	$165.72	$165.70	$165.70
Purchase #5	$175.45	3.870%	$182.2399	$182.24	$182.25	$182.20
Purchase #6	$224.84	5.792%	$237.8627	$237.86	$237.85	$237.90
Purchase #7	$30.60	9.436%	$33.4874	$33.49	$33.50	$33.50
7 purchase totals =	$1,000.53		$1,075.2572	$1,075.27	$1,075.25	$1,075.30