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	$175.33	12.137%	$196.6098	$196.61	$196.60	$196.60
Purchase #2	$120.59	12.373%	$135.5106	$135.51	$135.50	$135.50
Purchase #3	$225.83	5.521%	$238.2981	$238.30	$238.30	$238.30
Purchase #4	$91.63	12.640%	$103.212	$103.21	$103.20	$103.20
Purchase #5	$214.53	3.129%	$221.2426	$221.24	$221.25	$221.20
Purchase #6	$56.94	11.250%	$63.3458	$63.35	$63.35	$63.30
Purchase #7	$46.29	10.711%	$51.2481	$51.25	$51.25	$51.20
7 purchase totals =	$931.14		$1,009.4670	$1,009.47	$1,009.45	$1,009.30