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	$176.51	5.127%	$185.5597	$185.56	$185.55	$185.60
Purchase #2	$78.94	7.329%	$84.7255	$84.73	$84.75	$84.70
Purchase #3	$67.35	10.578%	$74.4743	$74.47	$74.45	$74.50
Purchase #4	$51.76	8.508%	$56.1637	$56.16	$56.15	$56.20
Purchase #5	$196.95	13.693%	$223.9184	$223.92	$223.90	$223.90
Purchase #6	$142.76	5.438%	$150.5233	$150.52	$150.50	$150.50
Purchase #7	$217.84	7.544%	$234.2738	$234.27	$234.25	$234.30
7 purchase totals =	$932.11		$1,009.6387	$1,009.63	$1,009.55	$1,009.70