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	$202.55	11.131%	$225.0958	$225.10	$225.10	$225.10
Purchase #2	$73.89	4.301%	$77.068	$77.07	$77.05	$77.10
Purchase #3	$169.41	3.126%	$174.7058	$174.71	$174.70	$174.70
Purchase #4	$155.34	10.358%	$171.4301	$171.43	$171.45	$171.40
Purchase #5	$123.84	6.276%	$131.6122	$131.61	$131.60	$131.60
Purchase #6	$164.72	8.156%	$178.1546	$178.15	$178.15	$178.20
Purchase #7	$90.63	10.457%	$100.1072	$100.11	$100.10	$100.10
7 purchase totals =	$980.38		$1,058.1737	$1,058.18	$1,058.15	$1,058.20