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	$84.65	3.300%	$87.4435	$87.44	$87.45	$87.40
Purchase #2	$123.51	10.428%	$136.3896	$136.39	$136.40	$136.40
Purchase #3	$201.31	7.709%	$216.829	$216.83	$216.85	$216.80
Purchase #4	$174.66	3.533%	$180.8307	$180.83	$180.85	$180.80
Purchase #5	$90.53	10.286%	$99.8419	$99.84	$99.85	$99.80
Purchase #6	$137.27	11.308%	$152.7925	$152.79	$152.80	$152.80
Purchase #7	$123.40	11.321%	$137.3701	$137.37	$137.35	$137.40
7 purchase totals =	$935.33		$1,011.4973	$1,011.49	$1,011.55	$1,011.40