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	$200.40	8.460%	$217.3538	$217.35	$217.35	$217.40
Purchase #2	$98.31	5.671%	$103.8852	$103.89	$103.90	$103.90
Purchase #3	$93.41	3.714%	$96.8792	$96.88	$96.90	$96.90
Purchase #4	$132.40	7.119%	$141.8256	$141.83	$141.85	$141.80
Purchase #5	$176.54	9.516%	$193.3395	$193.34	$193.35	$193.30
Purchase #6	$225.35	6.529%	$240.0631	$240.06	$240.05	$240.10
Purchase #7	$88.45	4.144%	$92.1154	$92.12	$92.10	$92.10
7 purchase totals =	$1,014.86		$1,085.4618	$1,085.47	$1,085.50	$1,085.50