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	$23.38	8.263%	$25.3119	$25.31	$25.30	$25.30
Purchase #2	$127.86	10.463%	$141.238	$141.24	$141.25	$141.20
Purchase #3	$98.86	3.446%	$102.2667	$102.27	$102.25	$102.30
Purchase #4	$155.51	12.694%	$175.2504	$175.25	$175.25	$175.30
Purchase #5	$176.34	3.489%	$182.4925	$182.49	$182.50	$182.50
Purchase #6	$232.58	3.365%	$240.4063	$240.41	$240.40	$240.40
Purchase #7	$90.98	10.807%	$100.8122	$100.81	$100.80	$100.80
7 purchase totals =	$905.51		$967.7780	$967.78	$967.75	$967.80