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	$162.64	9.118%	$177.4695	$177.47	$177.45	$177.50
Purchase #2	$77.66	3.489%	$80.3696	$80.37	$80.35	$80.40
Purchase #3	$84.47	11.429%	$94.1241	$94.12	$94.10	$94.10
Purchase #4	$78.60	4.320%	$81.9955	$82.00	$82.00	$82.00
Purchase #5	$159.97	12.453%	$179.8911	$179.89	$179.90	$179.90
Purchase #6	$64.64	10.652%	$71.5255	$71.53	$71.55	$71.50
Purchase #7	$40.56	3.410%	$41.9431	$41.94	$41.95	$41.90
7 purchase totals =	$668.54		$727.3184	$727.32	$727.30	$727.30