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	$203.41	10.786%	$225.3498	$225.35	$225.35	$225.30
Purchase #2	$154.36	9.256%	$168.6476	$168.65	$168.65	$168.60
Purchase #3	$236.26	9.811%	$259.4395	$259.44	$259.45	$259.40
Purchase #4	$175.61	10.810%	$194.5934	$194.59	$194.60	$194.60
Purchase #5	$188.90	4.200%	$196.8338	$196.83	$196.85	$196.80
Purchase #6	$31.36	3.825%	$32.5595	$32.56	$32.55	$32.60
Purchase #7	$96.95	10.812%	$107.4322	$107.43	$107.45	$107.40
7 purchase totals =	$1,086.85		$1,184.8558	$1,184.85	$1,184.90	$1,184.70