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	$121.82	3.277%	$125.812	$125.81	$125.80	$125.80
Purchase #2	$184.55	3.814%	$191.5887	$191.59	$191.60	$191.60
Purchase #3	$152.90	12.588%	$172.1471	$172.15	$172.15	$172.10
Purchase #4	$243.83	7.818%	$262.8926	$262.89	$262.90	$262.90
Purchase #5	$136.39	3.242%	$140.8118	$140.81	$140.80	$140.80
Purchase #6	$196.72	6.121%	$208.7612	$208.76	$208.75	$208.80
Purchase #7	$74.87	6.863%	$80.0083	$80.01	$80.00	$80.00
7 purchase totals =	$1,111.08		$1,182.0217	$1,182.02	$1,182.00	$1,182.00