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	$173.79	9.627%	$190.5208	$190.52	$190.50	$190.50
Purchase #2	$221.32	6.549%	$235.8142	$235.81	$235.80	$235.80
Purchase #3	$131.46	12.709%	$148.1673	$148.17	$148.15	$148.20
Purchase #4	$46.37	3.257%	$47.8803	$47.88	$47.90	$47.90
Purchase #5	$130.68	3.700%	$135.5152	$135.52	$135.50	$135.50
Purchase #6	$187.69	12.559%	$211.262	$211.26	$211.25	$211.30
Purchase #7	$84.40	7.579%	$90.7967	$90.80	$90.80	$90.80
7 purchase totals =	$975.71		$1,059.9565	$1,059.96	$1,059.90	$1,060.00