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	$94.75	13.817%	$107.8416	$107.84	$107.85	$107.80
Purchase #2	$74.80	10.376%	$82.5612	$82.56	$82.55	$82.60
Purchase #3	$110.44	11.530%	$123.1737	$123.17	$123.15	$123.20
Purchase #4	$221.83	11.285%	$246.8635	$246.86	$246.85	$246.90
Purchase #5	$74.95	4.602%	$78.3992	$78.40	$78.40	$78.40
Purchase #6	$132.83	11.302%	$147.8424	$147.84	$147.85	$147.80
Purchase #7	$138.83	9.612%	$152.1743	$152.17	$152.15	$152.20
7 purchase totals =	$848.43		$938.8559	$938.84	$938.80	$938.90