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	$82.32	12.193%	$92.3573	$92.36	$92.35	$92.40
Purchase #2	$153.46	7.146%	$164.4263	$164.43	$164.45	$164.40
Purchase #3	$182.32	10.108%	$200.7489	$200.75	$200.75	$200.70
Purchase #4	$85.94	9.752%	$94.3209	$94.32	$94.30	$94.30
Purchase #5	$106.55	7.195%	$114.2163	$114.22	$114.20	$114.20
Purchase #6	$67.93	3.451%	$70.2743	$70.27	$70.25	$70.30
Purchase #7	$35.88	5.729%	$37.9356	$37.94	$37.95	$37.90
7 purchase totals =	$714.40		$774.2796	$774.29	$774.25	$774.20