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	$168.55	13.473%	$191.2587	$191.26	$191.25	$191.30
Purchase #2	$161.65	8.354%	$175.1542	$175.15	$175.15	$175.20
Purchase #3	$20.49	4.530%	$21.4182	$21.42	$21.40	$21.40
Purchase #4	$98.52	7.223%	$105.6361	$105.64	$105.65	$105.60
Purchase #5	$197.33	12.835%	$222.6573	$222.66	$222.65	$222.70
Purchase #6	$105.48	8.334%	$114.2707	$114.27	$114.25	$114.30
Purchase #7	$195.25	6.749%	$208.4274	$208.43	$208.45	$208.40
7 purchase totals =	$947.27		$1,038.8226	$1,038.83	$1,038.80	$1,038.90