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	$105.45	13.372%	$119.5508	$119.55	$119.55	$119.60
Purchase #2	$117.67	6.551%	$125.3786	$125.38	$125.40	$125.40
Purchase #3	$223.97	7.825%	$241.4957	$241.50	$241.50	$241.50
Purchase #4	$144.96	13.369%	$164.3397	$164.34	$164.35	$164.30
Purchase #5	$186.98	4.833%	$196.0167	$196.02	$196.00	$196.00
Purchase #6	$209.57	6.781%	$223.7809	$223.78	$223.80	$223.80
Purchase #7	$221.85	11.720%	$247.8508	$247.85	$247.85	$247.90
7 purchase totals =	$1,210.45		$1,318.4132	$1,318.42	$1,318.45	$1,318.50