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	$216.47	6.134%	$229.7483	$229.75	$229.75	$229.70
Purchase #2	$178.94	10.149%	$197.1006	$197.10	$197.10	$197.10
Purchase #3	$97.55	7.813%	$105.1716	$105.17	$105.15	$105.20
Purchase #4	$164.64	10.802%	$182.4244	$182.42	$182.40	$182.40
Purchase #5	$86.25	9.565%	$94.4998	$94.50	$94.50	$94.50
Purchase #6	$153.47	13.646%	$174.4125	$174.41	$174.40	$174.40
Purchase #7	$119.56	7.556%	$128.594	$128.59	$128.60	$128.60
7 purchase totals =	$1,016.88		$1,111.9512	$1,111.94	$1,111.90	$1,111.90