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	$137.37	5.563%	$145.0119	$145.01	$145.00	$145.00
Purchase #2	$50.69	7.183%	$54.3311	$54.33	$54.35	$54.30
Purchase #3	$136.53	5.858%	$144.5279	$144.53	$144.55	$144.50
Purchase #4	$135.43	9.217%	$147.9126	$147.91	$147.90	$147.90
Purchase #5	$28.38	13.696%	$32.2669	$32.27	$32.25	$32.30
Purchase #6	$99.92	7.486%	$107.4	$107.40	$107.40	$107.40
Purchase #7	$73.57	6.661%	$78.4705	$78.47	$78.45	$78.50
7 purchase totals =	$661.89		$709.9209	$709.92	$709.90	$709.90