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	$147.39	13.837%	$167.7844	$167.78	$167.80	$167.80
Purchase #2	$88.27	9.490%	$96.6468	$96.65	$96.65	$96.60
Purchase #3	$243.55	10.614%	$269.4004	$269.40	$269.40	$269.40
Purchase #4	$195.86	4.711%	$205.087	$205.09	$205.10	$205.10
Purchase #5	$81.90	5.563%	$86.4561	$86.46	$86.45	$86.50
Purchase #6	$187.50	4.534%	$196.0013	$196.00	$196.00	$196.00
Purchase #7	$21.33	10.201%	$23.5059	$23.51	$23.50	$23.50
7 purchase totals =	$965.80		$1,044.8819	$1,044.89	$1,044.90	$1,044.90