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	$11.82	3.596%	$12.245	$12.25	$12.25	$12.20
Purchase #2	$184.98	13.102%	$209.2161	$209.22	$209.20	$209.20
Purchase #3	$6.93	13.199%	$7.8447	$7.84	$7.85	$7.80
Purchase #4	$179.36	9.697%	$196.7525	$196.75	$196.75	$196.80
Purchase #5	$123.38	11.444%	$137.4996	$137.50	$137.50	$137.50
Purchase #6	$224.94	13.128%	$254.4701	$254.47	$254.45	$254.50
Purchase #7	$235.73	4.258%	$245.7674	$245.77	$245.75	$245.80
7 purchase totals =	$967.14		$1,063.7954	$1,063.80	$1,063.75	$1,063.80