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	$37.53	10.659%	$41.5303	$41.53	$41.55	$41.50
Purchase #2	$96.74	9.445%	$105.8771	$105.88	$105.90	$105.90
Purchase #3	$106.67	13.317%	$120.8752	$120.88	$120.90	$120.90
Purchase #4	$177.41	10.499%	$196.0363	$196.04	$196.05	$196.00
Purchase #5	$191.89	13.186%	$217.1926	$217.19	$217.20	$217.20
Purchase #6	$12.39	13.775%	$14.0967	$14.10	$14.10	$14.10
Purchase #7	$67.31	4.299%	$70.2037	$70.20	$70.20	$70.20
7 purchase totals =	$689.94		$765.8119	$765.82	$765.90	$765.80