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	$55.78	7.508%	$59.968	$59.97	$59.95	$60.00
Purchase #2	$162.75	7.388%	$174.774	$174.77	$174.75	$174.80
Purchase #3	$91.73	8.304%	$99.3473	$99.35	$99.35	$99.30
Purchase #4	$7.25	6.452%	$7.7178	$7.72	$7.70	$7.70
Purchase #5	$132.83	9.195%	$145.0437	$145.04	$145.05	$145.00
Purchase #6	$80.68	8.215%	$87.3079	$87.31	$87.30	$87.30
Purchase #7	$142.75	7.692%	$153.7303	$153.73	$153.75	$153.70
7 purchase totals =	$673.77		$727.8890	$727.89	$727.85	$727.80