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	$95.96	13.787%	$109.19	$109.19	$109.20	$109.20
Purchase #2	$206.40	9.280%	$225.5539	$225.55	$225.55	$225.60
Purchase #3	$136.82	8.474%	$148.4141	$148.41	$148.40	$148.40
Purchase #4	$196.76	11.629%	$219.6412	$219.64	$219.65	$219.60
Purchase #5	$64.49	12.483%	$72.5403	$72.54	$72.55	$72.50
Purchase #6	$97.76	4.824%	$102.4759	$102.48	$102.50	$102.50
Purchase #7	$184.62	3.282%	$190.6792	$190.68	$190.70	$190.70
7 purchase totals =	$982.81		$1,068.4946	$1,068.49	$1,068.55	$1,068.50