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	$229.74	12.646%	$258.7929	$258.79	$258.80	$258.80
Purchase #2	$243.25	6.693%	$259.5307	$259.53	$259.55	$259.50
Purchase #3	$85.30	5.395%	$89.9019	$89.90	$89.90	$89.90
Purchase #4	$65.42	7.238%	$70.1551	$70.16	$70.15	$70.20
Purchase #5	$182.39	13.266%	$206.5859	$206.59	$206.60	$206.60
Purchase #6	$247.71	4.403%	$258.6167	$258.62	$258.60	$258.60
Purchase #7	$16.27	13.190%	$18.416	$18.42	$18.40	$18.40
7 purchase totals =	$1,070.08		$1,161.9992	$1,162.01	$1,162.00	$1,162.00