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	$125.61	5.764%	$132.8502	$132.85	$132.85	$132.90
Purchase #2	$195.47	5.450%	$206.1231	$206.12	$206.10	$206.10
Purchase #3	$109.61	5.179%	$115.2867	$115.29	$115.30	$115.30
Purchase #4	$181.25	13.139%	$205.0644	$205.06	$205.05	$205.10
Purchase #5	$213.95	11.662%	$238.9008	$238.90	$238.90	$238.90
Purchase #6	$108.56	8.574%	$117.8679	$117.87	$117.85	$117.90
Purchase #7	$78.76	4.807%	$82.546	$82.55	$82.55	$82.50
7 purchase totals =	$1,013.21		$1,098.6391	$1,098.64	$1,098.60	$1,098.70