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	$133.50	6.402%	$142.0467	$142.05	$142.05	$142.00
Purchase #2	$117.43	9.240%	$128.2805	$128.28	$128.30	$128.30
Purchase #3	$36.52	4.270%	$38.0794	$38.08	$38.10	$38.10
Purchase #4	$50.29	13.279%	$56.968	$56.97	$56.95	$57.00
Purchase #5	$164.42	4.163%	$171.2648	$171.26	$171.25	$171.30
Purchase #6	$98.88	5.709%	$104.5251	$104.53	$104.55	$104.50
Purchase #7	$140.86	9.518%	$154.2671	$154.27	$154.25	$154.30
7 purchase totals =	$741.90		$795.4316	$795.44	$795.45	$795.50