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	$150.42	3.273%	$155.3432	$155.34	$155.35	$155.30
Purchase #2	$180.64	8.184%	$195.4236	$195.42	$195.40	$195.40
Purchase #3	$37.46	3.626%	$38.8183	$38.82	$38.80	$38.80
Purchase #4	$223.94	3.495%	$231.7667	$231.77	$231.75	$231.80
Purchase #5	$245.67	7.649%	$264.4613	$264.46	$264.45	$264.50
Purchase #6	$55.71	11.853%	$62.3133	$62.31	$62.30	$62.30
Purchase #7	$92.58	6.715%	$98.7967	$98.80	$98.80	$98.80
7 purchase totals =	$986.42		$1,046.9231	$1,046.92	$1,046.85	$1,046.90