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	$184.83	7.729%	$199.1155	$199.12	$199.10	$199.10
Purchase #2	$164.46	7.310%	$176.482	$176.48	$176.50	$176.50
Purchase #3	$137.93	3.440%	$142.6748	$142.67	$142.65	$142.70
Purchase #4	$47.41	11.780%	$52.9949	$52.99	$53.00	$53.00
Purchase #5	$37.90	6.602%	$40.4022	$40.40	$40.40	$40.40
Purchase #6	$57.90	12.871%	$65.3523	$65.35	$65.35	$65.40
Purchase #7	$85.98	12.619%	$96.8298	$96.83	$96.85	$96.80
7 purchase totals =	$716.41		$773.8515	$773.84	$773.85	$773.90