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	$166.43	3.737%	$172.6495	$172.65	$172.65	$172.60
Purchase #2	$164.97	8.238%	$178.5602	$178.56	$178.55	$178.60
Purchase #3	$97.76	13.486%	$110.9439	$110.94	$110.95	$110.90
Purchase #4	$216.76	3.590%	$224.5417	$224.54	$224.55	$224.50
Purchase #5	$187.94	13.623%	$213.5431	$213.54	$213.55	$213.50
Purchase #6	$137.56	9.836%	$151.0904	$151.09	$151.10	$151.10
Purchase #7	$30.47	8.186%	$32.9643	$32.96	$32.95	$33.00
7 purchase totals =	$1,001.89		$1,084.2931	$1,084.28	$1,084.30	$1,084.20