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	$153.43	3.132%	$158.2354	$158.24	$158.25	$158.20
Purchase #2	$186.78	5.183%	$196.4608	$196.46	$196.45	$196.50
Purchase #3	$78.73	5.381%	$82.9665	$82.97	$82.95	$83.00
Purchase #4	$80.67	3.344%	$83.3676	$83.37	$83.35	$83.40
Purchase #5	$110.84	8.545%	$120.3113	$120.31	$120.30	$120.30
Purchase #6	$57.90	13.254%	$65.5741	$65.57	$65.55	$65.60
Purchase #7	$179.25	5.257%	$188.6732	$188.67	$188.65	$188.70
7 purchase totals =	$847.60		$895.5889	$895.59	$895.50	$895.70