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	$174.59	9.535%	$191.2372	$191.24	$191.25	$191.20
Purchase #2	$28.70	12.675%	$32.3377	$32.34	$32.35	$32.30
Purchase #3	$160.63	13.791%	$182.7825	$182.78	$182.80	$182.80
Purchase #4	$197.94	7.647%	$213.0765	$213.08	$213.10	$213.10
Purchase #5	$175.94	8.581%	$191.0374	$191.04	$191.05	$191.00
Purchase #6	$200.73	7.231%	$215.2448	$215.24	$215.25	$215.20
Purchase #7	$41.75	13.801%	$47.5119	$47.51	$47.50	$47.50
7 purchase totals =	$980.28		$1,073.2280	$1,073.23	$1,073.30	$1,073.10