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	$11.60	5.584%	$12.2477	$12.25	$12.25	$12.20
Purchase #2	$62.91	6.775%	$67.1722	$67.17	$67.15	$67.20
Purchase #3	$90.74	12.237%	$101.8439	$101.84	$101.85	$101.80
Purchase #4	$178.96	6.561%	$190.7016	$190.70	$190.70	$190.70
Purchase #5	$169.73	7.719%	$182.8315	$182.83	$182.85	$182.80
Purchase #6	$236.98	13.452%	$268.8585	$268.86	$268.85	$268.90
Purchase #7	$78.90	4.685%	$82.5965	$82.60	$82.60	$82.60
7 purchase totals =	$829.82		$906.2519	$906.25	$906.25	$906.20