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	$171.40	5.295%	$180.4756	$180.48	$180.50	$180.50
Purchase #2	$26.39	5.696%	$27.8932	$27.89	$27.90	$27.90
Purchase #3	$25.80	12.186%	$28.944	$28.94	$28.95	$28.90
Purchase #4	$161.70	4.287%	$168.6321	$168.63	$168.65	$168.60
Purchase #5	$249.38	10.360%	$275.2158	$275.22	$275.20	$275.20
Purchase #6	$82.25	4.132%	$85.6486	$85.65	$85.65	$85.60
Purchase #7	$5.89	13.326%	$6.6749	$6.67	$6.65	$6.70
7 purchase totals =	$722.81		$773.4842	$773.48	$773.50	$773.40