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	$184.98	8.588%	$200.8661	$200.87	$200.85	$200.90
Purchase #2	$31.76	11.413%	$35.3848	$35.38	$35.40	$35.40
Purchase #3	$66.99	6.307%	$71.2151	$71.22	$71.20	$71.20
Purchase #4	$178.39	13.766%	$202.9472	$202.95	$202.95	$202.90
Purchase #5	$224.64	5.273%	$236.4853	$236.49	$236.50	$236.50
Purchase #6	$182.37	7.710%	$196.4307	$196.43	$196.45	$196.40
Purchase #7	$115.47	7.273%	$123.8681	$123.87	$123.85	$123.90
7 purchase totals =	$984.60		$1,067.1973	$1,067.21	$1,067.20	$1,067.20