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	$133.91	6.384%	$142.4588	$142.46	$142.45	$142.50
Purchase #2	$163.43	10.459%	$180.5231	$180.52	$180.50	$180.50
Purchase #3	$176.68	4.342%	$184.3514	$184.35	$184.35	$184.40
Purchase #4	$52.49	9.225%	$57.3322	$57.33	$57.35	$57.30
Purchase #5	$79.59	12.496%	$89.5356	$89.54	$89.55	$89.50
Purchase #6	$113.63	10.375%	$125.4191	$125.42	$125.40	$125.40
Purchase #7	$162.56	3.496%	$168.2431	$168.24	$168.25	$168.20
7 purchase totals =	$882.29		$947.8633	$947.86	$947.85	$947.80