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	$196.25	11.143%	$218.1181	$218.12	$218.10	$218.10
Purchase #2	$99.74	12.659%	$112.3661	$112.37	$112.35	$112.40
Purchase #3	$76.37	8.685%	$83.0027	$83.00	$83.00	$83.00
Purchase #4	$125.87	4.486%	$131.5165	$131.52	$131.50	$131.50
Purchase #5	$156.39	6.320%	$166.2738	$166.27	$166.25	$166.30
Purchase #6	$187.37	12.206%	$210.2404	$210.24	$210.25	$210.20
Purchase #7	$36.45	5.199%	$38.345	$38.35	$38.35	$38.30
7 purchase totals =	$878.44		$959.8626	$959.87	$959.80	$959.80