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	$43.89	4.486%	$45.8589	$45.86	$45.85	$45.90
Purchase #2	$84.80	6.678%	$90.4629	$90.46	$90.45	$90.50
Purchase #3	$88.89	10.585%	$98.299	$98.30	$98.30	$98.30
Purchase #4	$164.67	3.168%	$169.8867	$169.89	$169.90	$169.90
Purchase #5	$180.67	7.825%	$194.8074	$194.81	$194.80	$194.80
Purchase #6	$15.89	4.794%	$16.6518	$16.65	$16.65	$16.70
Purchase #7	$160.63	13.867%	$182.9046	$182.90	$182.90	$182.90
7 purchase totals =	$739.44		$798.8713	$798.87	$798.85	$799.00