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	$145.84	7.163%	$156.2865	$156.29	$156.30	$156.30
Purchase #2	$148.40	12.481%	$166.9218	$166.92	$166.90	$166.90
Purchase #3	$169.64	12.225%	$190.3785	$190.38	$190.40	$190.40
Purchase #4	$6.37	7.206%	$6.829	$6.83	$6.85	$6.80
Purchase #5	$210.66	9.122%	$229.8764	$229.88	$229.90	$229.90
Purchase #6	$158.58	3.576%	$164.2508	$164.25	$164.25	$164.30
Purchase #7	$118.76	11.633%	$132.5754	$132.58	$132.60	$132.60
7 purchase totals =	$958.25		$1,047.1184	$1,047.13	$1,047.20	$1,047.20