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	$38.57	7.304%	$41.3872	$41.39	$41.40	$41.40
Purchase #2	$58.88	11.799%	$65.8273	$65.83	$65.85	$65.80
Purchase #3	$12.82	4.471%	$13.3932	$13.39	$13.40	$13.40
Purchase #4	$163.97	8.853%	$178.4863	$178.49	$178.50	$178.50
Purchase #5	$93.33	6.345%	$99.2518	$99.25	$99.25	$99.30
Purchase #6	$159.87	7.718%	$172.2088	$172.21	$172.20	$172.20
Purchase #7	$210.28	7.636%	$226.337	$226.34	$226.35	$226.30
7 purchase totals =	$737.72		$796.8916	$796.90	$796.95	$796.90