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	$18.59	5.252%	$19.5663	$19.57	$19.55	$19.60
Purchase #2	$240.45	5.237%	$253.0424	$253.04	$253.05	$253.00
Purchase #3	$155.63	8.196%	$168.3854	$168.39	$168.40	$168.40
Purchase #4	$236.67	11.474%	$263.8255	$263.83	$263.85	$263.80
Purchase #5	$43.55	6.342%	$46.3119	$46.31	$46.30	$46.30
Purchase #6	$246.47	3.597%	$255.3355	$255.34	$255.35	$255.30
Purchase #7	$39.33	8.445%	$42.6514	$42.65	$42.65	$42.70
7 purchase totals =	$980.69		$1,049.1184	$1,049.13	$1,049.15	$1,049.10