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	$92.88	10.856%	$102.9631	$102.96	$102.95	$103.00
Purchase #2	$250.97	13.546%	$284.9664	$284.97	$284.95	$285.00
Purchase #3	$120.30	6.582%	$128.2181	$128.22	$128.20	$128.20
Purchase #4	$92.50	6.355%	$98.3784	$98.38	$98.40	$98.40
Purchase #5	$198.32	7.803%	$213.7949	$213.79	$213.80	$213.80
Purchase #6	$118.39	4.331%	$123.5175	$123.52	$123.50	$123.50
Purchase #7	$182.84	8.601%	$198.5661	$198.57	$198.55	$198.60
7 purchase totals =	$1,056.20		$1,150.4045	$1,150.41	$1,150.35	$1,150.50