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	$160.91	3.326%	$166.2619	$166.26	$166.25	$166.30
Purchase #2	$113.33	3.223%	$116.9826	$116.98	$117.00	$117.00
Purchase #3	$173.98	3.298%	$179.7179	$179.72	$179.70	$179.70
Purchase #4	$231.28	12.629%	$260.4884	$260.49	$260.50	$260.50
Purchase #5	$58.27	13.697%	$66.2512	$66.25	$66.25	$66.30
Purchase #6	$78.77	10.344%	$86.918	$86.92	$86.90	$86.90
Purchase #7	$131.58	6.554%	$140.2038	$140.20	$140.20	$140.20
7 purchase totals =	$948.12		$1,016.8238	$1,016.82	$1,016.80	$1,016.90