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	$248.85	5.256%	$261.9296	$261.93	$261.95	$261.90
Purchase #2	$105.90	6.479%	$112.7613	$112.76	$112.75	$112.80
Purchase #3	$123.67	4.187%	$128.8481	$128.85	$128.85	$128.80
Purchase #4	$206.68	7.326%	$221.8214	$221.82	$221.80	$221.80
Purchase #5	$136.42	3.528%	$141.2329	$141.23	$141.25	$141.20
Purchase #6	$91.65	4.799%	$96.0483	$96.05	$96.05	$96.00
Purchase #7	$110.89	11.214%	$123.3252	$123.33	$123.35	$123.30
7 purchase totals =	$1,024.06		$1,085.9668	$1,085.97	$1,086.00	$1,085.80