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	$104.63	10.354%	$115.4634	$115.46	$115.45	$115.50
Purchase #2	$218.31	13.666%	$248.1442	$248.14	$248.15	$248.10
Purchase #3	$180.55	4.745%	$189.1171	$189.12	$189.10	$189.10
Purchase #4	$63.81	9.270%	$69.7252	$69.73	$69.75	$69.70
Purchase #5	$176.75	6.462%	$188.1716	$188.17	$188.15	$188.20
Purchase #6	$163.89	11.128%	$182.1277	$182.13	$182.15	$182.10
Purchase #7	$100.59	3.255%	$103.8642	$103.86	$103.85	$103.90
7 purchase totals =	$1,008.53		$1,096.6134	$1,096.61	$1,096.60	$1,096.60