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	$190.71	5.577%	$201.3459	$201.35	$201.35	$201.30
Purchase #2	$49.65	13.637%	$56.4208	$56.42	$56.40	$56.40
Purchase #3	$114.56	6.644%	$122.1714	$122.17	$122.15	$122.20
Purchase #4	$182.64	7.465%	$196.2741	$196.27	$196.25	$196.30
Purchase #5	$96.38	7.404%	$103.516	$103.52	$103.50	$103.50
Purchase #6	$249.35	12.797%	$281.2593	$281.26	$281.25	$281.30
Purchase #7	$231.88	10.338%	$255.8518	$255.85	$255.85	$255.90
7 purchase totals =	$1,115.17		$1,216.8393	$1,216.84	$1,216.75	$1,216.90