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	$179.43	9.520%	$196.5117	$196.51	$196.50	$196.50
Purchase #2	$103.46	4.528%	$108.1447	$108.14	$108.15	$108.10
Purchase #3	$182.79	4.485%	$190.9881	$190.99	$191.00	$191.00
Purchase #4	$158.94	4.136%	$165.5138	$165.51	$165.50	$165.50
Purchase #5	$51.82	9.293%	$56.6356	$56.64	$56.65	$56.60
Purchase #6	$47.52	9.367%	$51.9712	$51.97	$51.95	$52.00
Purchase #7	$80.32	9.102%	$87.6307	$87.63	$87.65	$87.60
7 purchase totals =	$804.28		$857.3958	$857.39	$857.40	$857.30