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	$186.77	12.371%	$209.8753	$209.88	$209.90	$209.90
Purchase #2	$126.64	4.180%	$131.9336	$131.93	$131.95	$131.90
Purchase #3	$194.49	9.121%	$212.2294	$212.23	$212.25	$212.20
Purchase #4	$218.76	5.674%	$231.1724	$231.17	$231.15	$231.20
Purchase #5	$187.76	4.612%	$196.4195	$196.42	$196.40	$196.40
Purchase #6	$152.75	3.736%	$158.4567	$158.46	$158.45	$158.50
Purchase #7	$183.41	12.387%	$206.129	$206.13	$206.15	$206.10
7 purchase totals =	$1,250.58		$1,346.2159	$1,346.22	$1,346.25	$1,346.20