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	$55.87	10.147%	$61.5391	$61.54	$61.55	$61.50
Purchase #2	$152.93	7.420%	$164.2774	$164.28	$164.30	$164.30
Purchase #3	$18.48	11.153%	$20.5411	$20.54	$20.55	$20.50
Purchase #4	$10.67	10.473%	$11.7875	$11.79	$11.80	$11.80
Purchase #5	$186.80	3.455%	$193.2539	$193.25	$193.25	$193.30
Purchase #6	$127.57	3.557%	$132.1077	$132.11	$132.10	$132.10
Purchase #7	$57.68	7.280%	$61.8791	$61.88	$61.90	$61.90
7 purchase totals =	$610.00		$645.3858	$645.39	$645.45	$645.40