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	$29.83	7.820%	$32.1627	$32.16	$32.15	$32.20
Purchase #2	$20.70	11.613%	$23.1039	$23.10	$23.10	$23.10
Purchase #3	$98.75	10.746%	$109.3617	$109.36	$109.35	$109.40
Purchase #4	$9.95	13.728%	$11.3159	$11.32	$11.30	$11.30
Purchase #5	$29.86	6.263%	$31.7301	$31.73	$31.75	$31.70
Purchase #6	$103.77	10.112%	$114.2632	$114.26	$114.25	$114.30
Purchase #7	$125.64	13.438%	$142.5235	$142.52	$142.50	$142.50
7 purchase totals =	$418.50		$464.4610	$464.45	$464.40	$464.50