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	$137.48	4.581%	$143.778	$143.78	$143.80	$143.80
Purchase #2	$94.61	6.550%	$100.807	$100.81	$100.80	$100.80
Purchase #3	$85.72	11.306%	$95.4115	$95.41	$95.40	$95.40
Purchase #4	$136.38	4.161%	$142.0548	$142.05	$142.05	$142.10
Purchase #5	$139.39	5.518%	$147.0815	$147.08	$147.10	$147.10
Purchase #6	$246.91	10.845%	$273.6874	$273.69	$273.70	$273.70
Purchase #7	$146.38	6.205%	$155.4629	$155.46	$155.45	$155.50
7 purchase totals =	$986.87		$1,058.2831	$1,058.28	$1,058.30	$1,058.40