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	$77.84	9.447%	$85.1935	$85.19	$85.20	$85.20
Purchase #2	$216.42	6.210%	$229.8597	$229.86	$229.85	$229.90
Purchase #3	$81.71	11.629%	$91.2121	$91.21	$91.20	$91.20
Purchase #4	$196.31	7.422%	$210.8801	$210.88	$210.90	$210.90
Purchase #5	$144.74	8.769%	$157.4323	$157.43	$157.45	$157.40
Purchase #6	$174.96	7.784%	$188.5789	$188.58	$188.60	$188.60
Purchase #7	$119.44	11.262%	$132.8913	$132.89	$132.90	$132.90
7 purchase totals =	$1,011.42		$1,096.0479	$1,096.04	$1,096.10	$1,096.10