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	$201.30	6.499%	$214.3825	$214.38	$214.40	$214.40
Purchase #2	$81.36	9.673%	$89.23	$89.23	$89.25	$89.20
Purchase #3	$226.71	12.611%	$255.3004	$255.30	$255.30	$255.30
Purchase #4	$158.59	3.643%	$164.3674	$164.37	$164.35	$164.40
Purchase #5	$126.87	4.129%	$132.1085	$132.11	$132.10	$132.10
Purchase #6	$198.73	7.314%	$213.2651	$213.27	$213.25	$213.30
Purchase #7	$72.77	10.310%	$80.2726	$80.27	$80.25	$80.30
7 purchase totals =	$1,066.33		$1,148.9265	$1,148.93	$1,148.90	$1,149.00