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	$242.28	7.859%	$261.3208	$261.32	$261.30	$261.30
Purchase #2	$95.27	10.153%	$104.9428	$104.94	$104.95	$104.90
Purchase #3	$182.89	9.409%	$200.0981	$200.10	$200.10	$200.10
Purchase #4	$198.84	6.724%	$212.21	$212.21	$212.20	$212.20
Purchase #5	$151.40	10.669%	$167.5529	$167.55	$167.55	$167.60
Purchase #6	$87.39	8.737%	$95.0253	$95.03	$95.05	$95.00
Purchase #7	$99.50	9.637%	$109.0888	$109.09	$109.10	$109.10
7 purchase totals =	$1,057.57		$1,150.2387	$1,150.24	$1,150.25	$1,150.20