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	$126.33	8.867%	$137.5317	$137.53	$137.55	$137.50
Purchase #2	$156.41	6.327%	$166.3061	$166.31	$166.30	$166.30
Purchase #3	$136.47	4.685%	$142.8636	$142.86	$142.85	$142.90
Purchase #4	$183.74	7.155%	$196.8866	$196.89	$196.90	$196.90
Purchase #5	$34.75	9.627%	$38.0954	$38.10	$38.10	$38.10
Purchase #6	$79.80	4.509%	$83.3982	$83.40	$83.40	$83.40
Purchase #7	$161.30	12.544%	$181.5335	$181.53	$181.55	$181.50
7 purchase totals =	$878.80		$946.6151	$946.62	$946.65	$946.60