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	$98.44	11.258%	$109.5224	$109.52	$109.50	$109.50
Purchase #2	$91.35	11.259%	$101.6351	$101.64	$101.65	$101.60
Purchase #3	$216.86	5.111%	$227.9437	$227.94	$227.95	$227.90
Purchase #4	$134.73	7.536%	$144.8833	$144.88	$144.90	$144.90
Purchase #5	$175.39	11.807%	$196.0983	$196.10	$196.10	$196.10
Purchase #6	$242.70	11.195%	$269.8703	$269.87	$269.85	$269.90
Purchase #7	$250.87	3.109%	$258.6695	$258.67	$258.65	$258.70
7 purchase totals =	$1,210.34		$1,308.6226	$1,308.62	$1,308.60	$1,308.60