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	$53.50	10.533%	$59.1352	$59.14	$59.15	$59.10
Purchase #2	$150.94	5.350%	$159.0153	$159.02	$159.00	$159.00
Purchase #3	$219.98	3.263%	$227.1579	$227.16	$227.15	$227.20
Purchase #4	$43.77	5.690%	$46.2605	$46.26	$46.25	$46.30
Purchase #5	$207.33	8.422%	$224.7913	$224.79	$224.80	$224.80
Purchase #6	$123.67	10.580%	$136.7543	$136.75	$136.75	$136.80
Purchase #7	$145.31	7.281%	$155.89	$155.89	$155.90	$155.90
7 purchase totals =	$944.50		$1,009.0045	$1,009.01	$1,009.00	$1,009.10