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	$123.51	11.421%	$137.6161	$137.62	$137.60	$137.60
Purchase #2	$191.72	4.680%	$200.6925	$200.69	$200.70	$200.70
Purchase #3	$37.35	4.811%	$39.1469	$39.15	$39.15	$39.10
Purchase #4	$117.54	11.614%	$131.1911	$131.19	$131.20	$131.20
Purchase #5	$240.55	11.683%	$268.6535	$268.65	$268.65	$268.70
Purchase #6	$235.70	4.565%	$246.4597	$246.46	$246.45	$246.50
Purchase #7	$196.78	7.579%	$211.694	$211.69	$211.70	$211.70
7 purchase totals =	$1,143.15		$1,235.4538	$1,235.45	$1,235.45	$1,235.50