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	$225.51	7.863%	$243.2419	$243.24	$243.25	$243.20
Purchase #2	$107.63	4.401%	$112.3668	$112.37	$112.35	$112.40
Purchase #3	$79.97	7.444%	$85.923	$85.92	$85.90	$85.90
Purchase #4	$250.28	10.534%	$276.6445	$276.64	$276.65	$276.60
Purchase #5	$131.82	5.692%	$139.3232	$139.32	$139.30	$139.30
Purchase #6	$42.88	11.604%	$47.8558	$47.86	$47.85	$47.90
Purchase #7	$156.84	9.565%	$171.8417	$171.84	$171.85	$171.80
7 purchase totals =	$994.93		$1,077.1969	$1,077.19	$1,077.15	$1,077.10