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	$193.90	6.270%	$206.0575	$206.06	$206.05	$206.10
Purchase #2	$182.60	12.443%	$205.3209	$205.32	$205.30	$205.30
Purchase #3	$200.37	4.606%	$209.599	$209.60	$209.60	$209.60
Purchase #4	$57.94	10.667%	$64.1205	$64.12	$64.10	$64.10
Purchase #5	$123.89	7.206%	$132.8175	$132.82	$132.80	$132.80
Purchase #6	$59.35	10.227%	$65.4197	$65.42	$65.40	$65.40
Purchase #7	$182.97	9.368%	$200.1106	$200.11	$200.10	$200.10
7 purchase totals =	$1,001.02		$1,083.4457	$1,083.45	$1,083.35	$1,083.40