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	$138.26	10.264%	$152.451	$152.45	$152.45	$152.50
Purchase #2	$143.46	4.753%	$150.2787	$150.28	$150.30	$150.30
Purchase #3	$13.29	7.654%	$14.3072	$14.31	$14.30	$14.30
Purchase #4	$179.83	9.280%	$196.5182	$196.52	$196.50	$196.50
Purchase #5	$21.29	7.182%	$22.819	$22.82	$22.80	$22.80
Purchase #6	$195.73	6.447%	$208.3487	$208.35	$208.35	$208.30
Purchase #7	$162.93	8.279%	$176.419	$176.42	$176.40	$176.40
7 purchase totals =	$854.79		$921.1418	$921.15	$921.10	$921.10