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	$78.48	5.190%	$82.5531	$82.55	$82.55	$82.60
Purchase #2	$190.59	12.576%	$214.5586	$214.56	$214.55	$214.60
Purchase #3	$158.82	3.869%	$164.9647	$164.96	$164.95	$165.00
Purchase #4	$226.84	10.407%	$250.4472	$250.45	$250.45	$250.40
Purchase #5	$242.82	10.753%	$268.9304	$268.93	$268.95	$268.90
Purchase #6	$184.70	3.231%	$190.6677	$190.67	$190.65	$190.70
Purchase #7	$42.59	3.652%	$44.1454	$44.15	$44.15	$44.10
7 purchase totals =	$1,124.84		$1,216.2671	$1,216.27	$1,216.25	$1,216.30