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	$88.31	3.765%	$91.6349	$91.63	$91.65	$91.60
Purchase #2	$214.31	11.396%	$238.7328	$238.73	$238.75	$238.70
Purchase #3	$161.78	6.625%	$172.4979	$172.50	$172.50	$172.50
Purchase #4	$202.87	3.786%	$210.5507	$210.55	$210.55	$210.60
Purchase #5	$245.38	5.624%	$259.1802	$259.18	$259.20	$259.20
Purchase #6	$131.41	8.661%	$142.7914	$142.79	$142.80	$142.80
Purchase #7	$38.45	4.689%	$40.2529	$40.25	$40.25	$40.30
7 purchase totals =	$1,082.51		$1,155.6408	$1,155.63	$1,155.70	$1,155.70