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	$50.59	3.267%	$52.2428	$52.24	$52.25	$52.20
Purchase #2	$213.94	5.602%	$225.9249	$225.92	$225.90	$225.90
Purchase #3	$123.47	6.182%	$131.1029	$131.10	$131.10	$131.10
Purchase #4	$43.48	9.384%	$47.5602	$47.56	$47.55	$47.60
Purchase #5	$130.63	12.764%	$147.3036	$147.30	$147.30	$147.30
Purchase #6	$118.71	10.420%	$131.0796	$131.08	$131.10	$131.10
Purchase #7	$145.96	3.404%	$150.9285	$150.93	$150.95	$150.90
7 purchase totals =	$826.78		$886.1425	$886.13	$886.15	$886.10