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	$11.62	5.577%	$12.268	$12.27	$12.25	$12.30
Purchase #2	$146.26	5.649%	$154.5222	$154.52	$154.50	$154.50
Purchase #3	$246.72	13.674%	$280.4565	$280.46	$280.45	$280.50
Purchase #4	$17.48	10.395%	$19.297	$19.30	$19.30	$19.30
Purchase #5	$61.33	10.398%	$67.7071	$67.71	$67.70	$67.70
Purchase #6	$183.34	10.788%	$203.1187	$203.12	$203.10	$203.10
Purchase #7	$243.76	12.158%	$273.3963	$273.40	$273.40	$273.40
7 purchase totals =	$910.51		$1,010.7658	$1,010.78	$1,010.70	$1,010.80